Part 68
[155] This may be partially seen in the section, fig. 1, of Balanus, on the same plate (25) with the figure of Proteolepas; here (bearing in mind that Balanus is a much modified form) (_z_) shows the pupal antennæ, within which, whilst young, the cement-ducts are included, and are directly continuous with the layer of branching ovarian cæca (_g_), which are prolonged up to the ovaria as a pair of simple tubes (only one being here represented), entering the body above the upper margin of the prosoma (_c_). The prosoma of Balanus, I may add, answers to the segment ^2 _t_ in fig. 7 of Proteolepas; (_e_) the mouth in Balanus, of course corresponding with (_m_) the mouth of Proteolepas; the segment ^1 _c_ and ^2 _t_ of the latter, are in Balanus aborted or confluent, at least on the ventral surface; and, lastly, the whole great shell of Balanus, the sack with its muscles and the branchiæ, and the opercular valves with their muscles, are all represented in Proteolepas merely by the outer membrane of the two threads (_g_), which enter the pupal antennæ!
_Secondly_: the external membrane of the two threads, investing the two cement-ducts, it should be remembered, is not moulted, and is added to during growth (being lined internally by corium), only round the upper, collar-like edge.
_Thirdly_: the external covering or carapace of every young cirripede, at the period of its metamorphosis, enters, at its lower end, the cemented antennæ, in the form of two short tubular prolongations, by which alone, at first, the cirripede adheres to the surface of attachment; within these prolongations the cement-ducts are included. I have, moreover, seen instances, as in _Conchoderma aurita_ and in the male of Ibla and Alcippe, in which these tubular prolongations, lined internally by corium, were increased a little in length, so as to form a trouser-like termination to the peduncle. That the forked extremity should be a little more developed, and so be converted into a pair of short tubular threads, cannot be considered as very improbable.
_Fourthly_: in the male Ibla the capitulum is so much atrophied that it does not enclose the thorax or mouth, but still an elongated support or peduncle is left. But it would be no very violent assumption to imagine the peduncle, which does not essentially differ from the capitulum, to become likewise rudimental,--to grow smaller and smaller, and shorter and shorter, till the merest remnant was left at the spot where it entered the cemented antennæ. And in the last paragraph it has been shown that it would be no violent assumption to imagine this lower end of the peduncle, where it enters the antennæ, developed into two short thread-like prolongations.
_Lastly_: it is certain, from the existence of the prehensile antennæ, that Proteolepas was developed within a pupa, probably differing in no very essential respect from the pupæ of other cirripedes. Therefore, in accordance with all analogy, we may believe that the position[156] of the young Proteolepas (probably much coiled up, with a deep fold close under the mouth) within the pupa, the general form and structure of the latter, and the course of the cement-ducts, did not _essentially_ differ from the imaginary figure given, Pl. 25, fig. 6. Now, at the period of the metamorphosis, let us imagine that no general covering or carapace was formed, except a small portion on the ventral surface, round the cemented antennæ. Let us further suppose this remnant to be specially developed (as in the case of some cirripedes) into a short trouser-like prolongation, entering the antennæ; and subsequently, in accordance with the almost universal laws of growth in cirripedes, that this portion was never moulted, but continued to be added to, during growth, only at its upper end. By this means we should produce every leading peculiarity of the _Proteolepas bivincta_. As this parasite lives within the sack of another cirripede, and is protected by the capitulum of the latter, we can understand, in accordance with the usual admirable economy of nature, the absence of any general covering for its body. We can now, also, understand the structure and manner of growth of the two threads by which it is bound to its prey; and the connection, at first so strange and perplexing, between the old pupal antennæ and the second segment of the thorax. I am convinced that no other explanation than that here given, will accord with the relations of the several parts and organs of Proteolepas. Consequently, I fully believe that we here see an articulate animal in which the whole of the three anterior segments of the head have been, during the act of metamorphosis, absolutely aborted, with the exception of a mere rudiment on the ventral surface, near the anterior end, round the old antennæ, and which rudiment has been specially developed as a covering for the two cement-ducts. As the pupal antennæ are, homologically, the second pair of antennæ, we may further infer that this modified remnant of the carapace, investing the two threads, belongs to the third cephalic segment.
[156] Any one who has not specially attended to the metamorphoses of ordinary cirripedes, who looks at the imaginary figure of the young Proteolepas, will feel much surprise at the relative positions of the parts; for the mouth and the first and even second segments of the body stand posteriorly (_i. e._ above in the figure) to the succeeding segments of the body, in relation to the carapace of the pupa; but this is only in accordance with the remarkable change in position (as explained in the introduction, p. 123, pl. 30, fig. 2), amounting almost to inversion, which the whole thorax of every young cirripede undergoes within the pupa, whilst the anterior cephalic portions and general covering are developed conformably with the pupal carapace, whence it arises that the _dorsal_ surface of that part of the thorax immediately succeeding the mouth becomes attached to the _ventral_ internal surface of the carapace. I believe that the peculiar flattened dorsal outline of the first two segments of the body of Proteolepas is due to these parts having been formed in contact (as represented in pl. 25, fig. 6) with the straight ventral surface of the carapace of the pupa. To place the young Proteolepas, and at the same time the carapace of the pupa, with all the parts in proper homological sequence, it would be necessary to seize the posterior end of the abdomen (_a_), and pull till the dorsal surfaces of the first and second segments of the body, separated from the ventral internal surface of the carapace, and stood posteriorly (_i. e._ above in figure) to the mouth, which latter would thus also have to rotate a quarter of a circle, so that the orifice would come to be directed outwards. Then every part would stand, in accordance with the archetype crustacean structure, in due order; but the three confluent anterior cephalic segments, forming the front part and carapace of the pupa, would, as in the case of all cirripedes, be of disproportionately large size in relation to the rest of the body.
SYNOPSIS
ET
INDEX SYSTEMATICUS.
_Ordinum, Familiarum, et Generum Cirripediorum et recentium et fossilium._
CLASSIS CRUSTACEA.
Sub-classis CIRRIPEDIA.
Crustacea ex anteriore capitis parte defixa, cæmento in hunc usum ex ovariorum portione ad id specialiter modificatâ emisso. Archetypus è segmentis 17 compositus, quorum 3 priora magna, in carapacem sæpissimè conformata, quæ non omnino exuitur et varios motus efficit: antennæ nullæ: oculi rudimentarii: os prominens, formatum è labro, palpis, mandibulis, et duobus maxillarum paribus, quæ omnia partim confluunt: thorax ad superficiem internam sternalem carapacis affixus, plerumque cum membrorum captantium biramorum, multiarticulorum paribus 6: abdomen plerumque rudimentarium: branchiæ, si quæ adsunt, ad inferiora carapacis latera affixæ: plerumque bisexualia; in unisexualibus, mares fœminis parasitice inserti: penis unicus, plerumque probosciformis, ad posteriorem abdominis extremitatem situs: oviductus nulli: metamorphoses multiplices.
ORDO I. THORACICA. (Darwin, 'Balanidæ,' p. 30.)
Cirripedia quibus pro carapace est aut capitulum pedunculatum, aut testa operculata cum basi. Corpus è 6 thoracicis segmentis, ferè cum 6 cirrorum paribus, constat. Abdomen rudimentarium, sed sæpe cum appendiculis caudalibus. Oris labrum motus proprios non efficit. Larva primò monocula cum 3 crurum paribus, postremò binocula cum 6 crurum thoracicorum paribus.
Familia 1. BALANIDÆ. (Darwin, 'Balanidæ,' p. 33.)
Cirripedia sine pedunculo: scuta et terga musculis depressoribus instructa: reliquæ testæ valvæ inter se immobiliter conjunctæ.
Sub-Familia 1. BALANINÆ. (Darwin, 'Balanidæ,' p. 175.)
Rostrum cum radiis, sed sine alis; valvæ testæ laterales omnes, ex uno latere alis, ex altero radiis instructæ: parietes ferè aut porosi aut ad interiorem superficiem longitudinaliter costati.
[_Sectio_ †.]
Scutum et tergum inter se articulata aut mutuò interclusa: branchiarum unaquæque ex unicâ plicâ constat.
1. _Genus_--BALANUS, _Auctorum_. (Darwin, 'Balanidæ,' p. 177.)
Valvæ testæ 6; basis calcarea aut membranacea; valvæ operculares subtriangulares.
2. _Sub-Genus_--ACASTA, _Leach_. (Darwin, 'Balanidæ,' p. 302.)
Valvæ testæ 6; parietes et basis non porosa; basis calcarea, cyathiformis, non elongata. Spongiis, aut rarò Isidis cortici, affixa.
3. _Genus_--TETRACLITA, _Schumacher_. (Darwin, 'Balanidæ,' p. 321.)
Valvæ testæ 4; interdum inter se externè confluentes: parietes poris perforati, multis plerumque seriebus; basis plana, irregularis, calcarea aut membranacea.
4. _Genus_--ELMINIUS, _Leach_. (Darwin, 'Balanidæ,' p. 345.)
Valvæ testæ 4; parietes non porosi; basis membranacea.
5. _Genus_--PYRGOMA, _Leach_. (Darwin, 'Balanidæ,' p. 354.)
Valvæ testæ in unam confluentes; basis cyathiformis aut subcylindrica, coraliis affixa.
6. _Sub-Genus_--CREUSIA, _Leach_. (Darwin, 'Balanidæ,' p. 375.)
Valvæ testæ 4, radiis instructæ; basis cyathiformis, coraliis affixa.
7. _Genus_--CHELONOBIA, _Leach_. (Darwin, 'Balanidæ,' p. 382.)
Valvæ testæ admodum crassæ, 6; sed ex iis, valva rostralis intùs è tribus valvis rudimentariis conjunctis constat; basis membranacea; scuta angusta, tergis cristâ articulari corneâ conjuncta.
[_Sectio_ ††.]
Scutum et tergum (ubi ambo adsunt) non inter se articulata; basis membranacea; parietes sæpe profundè plicati, laminâ exteriore, ad basin versâ, plerumque imperfectâ; branchiarum unaquæque e duobus plicis constat. Testa vertebratis vivis affixa.
8. _Genus_--CORONULA, _Lamarck_. (Darwin, 'Balanidæ,' p. 397.)
Valvæ testæ 6; æquali latitudine; parietes tenues, profundè plicati, plicis cavitates infrà solùm apertas efficientibus; valvæ operculares orificio testæ multo minores. Cetaceis affixa.
9. _Genus_--PLATYLEPAS, _J. E. Gray_. (Darwin, 'Balanidæ,' p. 424.)
Valvæ testæ 6; unaquæque bilobata et intùs producta, ita ut 6 medias costas longitudinales efficiant, quæ basin membranaceam extrorsùs convexam sustinent.
10. _Genus_--TUBICINELLA, _Lamarck_. (Darwin, 'Balanidæ,' p. 430.)
Valvæ testæ 6, æquali latitudine; testa subcylindrica, orificio latiore quam basis, pluribus cristis transversis virgata. Cetaceis affixa.
11. _Genus_--XENOBALANUS, _Steenstrup_. (Darwin, 'Balanidæ,' p. 438.)
Testa pæne rudimentaria, stelliformis, è valvis 6 formata, è quarum medio corpus longum pedunculiforme exoritur; valvæ operculares absunt. Cetaceis affixus.
Sub-Familia 2. CHTHAMALINÆ. (Darwin, 'Balanidæ,' p. 446.)
Rostrum cum alis sed sine radiis; valvæ rostro-laterales utrinque sine alis; parietes non porosi.
12. _Genus_--CHTHAMALUS, _Ranzani_. (Darwin, 'Balanidæ,' p. 447.)
Valvæ testæ 6; basis membranacea, sed interdum ad speciem calcarea, ideò quod parietes inflectuntur.
13. _Genus_--CHAMÆSIPHO, _Darwin_. ('Balanidæ' p. 470.)
Valvæ testæ 4, suturis sæpe admodùm obliteratis; basis membranacea.
14. _Genus_--PACHYLASMA, _Darwin_. ('Balanidæ,' p. 475.)
Valvæ testæ, conchâ recenter natâ, 8; adultâ aut 6, aut ad speciem 4, ideò quod valvæ laterales arctè conjunguntur; basis calcarea.
15. _Genus_--OCTOMERIS, _G. B. Sowerby_. (Darwin, 'Balanidæ,' p. 482.)
Valvæ testæ 8; radii marginibus crenatis; basis membranacea.
16. _Genus_--CATOPHRAGMUS, _G. B. Sowerby_. (Darwin, 'Balanidæ,' p. 485.)
Valvæ testæ interiores 8, cum pluribus exterioribus parvarum supplementalium valvarum verticillis; basis aut membranacea aut calcarea.
Familia 2. VERRUCIDÆ. (Darwin, 'Balanidæ,' p. 495.)
Cirripedia sine pedunculo; scuta et terga, musculis depressoribus non instructa, ex uno latere tantum mobilia, ex altero cum carinâ et rostro in testam asymmetricam immobiliter conjuncta.
1. _Genus_--VERRUCA, _Schumacher_. (Darwin, 'Balanidæ,' p. 496.)
Familia 3. LEPADIDÆ. (Darwin, 'Lepadidæ,' p. 8, et 'Balanidæ,' p. 526.)
Cirripedia pedunculo flexili, musculis instructo; scuta et terga (si qua adsunt) musculis depressoribus non instructa; reliquæ valvæ (si quæ adsunt) in annulum immobilem non conjunctæ.
1. _Genus_--LEPAS, _Linn._ (Darwin, 'Lepadidæ,' p. 67.)
Valvæ 5, approximatæ; carina sursùm inter terga extensa, deorsùm aut furcâ infossâ aut disco externo terminata; scuta subtriangula, umbonibus ad angulum rostralem positis.
2. _Genus_--PŒCILASMA, _Darwin_. ('Lepadidæ,' p. 99.)
Valvæ 3, 5, aut 7, approximatæ; carina solùm ad basales apices tergorum extensa, termino basali aut truncato aut in discum profunde infossum producto; scuta pænè ovalia, umbonibus ad angulum rostralem positis.
3. _Genus_--DICHELASPIS, _Darwin_. ('Lepadidæ,' p. 115.)
Valvæ 5, quæ ferè pro septem haberi possent, scuto in segmenta planè duo, ad angulum autem rostralem conjuncta, diviso; carina plerumque sursum inter terga extensa, deorsum aut disco infosso aut furcâ aut calyce terminata.
4. _Genus_--OXYNASPIS, _Darwin_. ('Lepadidæ,' p. 133.)
Valvæ 5, approximatæ; scutorum umbones in medio marginis occludentis positi; carina rectangulè flexa, sursùm inter terga extensa, termino basali simpliciter concavo.
5. _Genus_--CONCHODERMA, _Olfers_. (Darwin, 'Lepadidæ,' p. 136.)
Valvæ 2 ad 5, minutæ, inter se remotæ; scuta bi- aut tri-lobata, umbonibus in medio marginis occludentis positis; carina arcuata, terminis utrinque pæne similibus.
6. _Genus_--ALEPAS, _S. Rang_. (Darwin, 'Lepadidæ,' p. 156.)
Capitulum aut sine valvis, aut scutis corneis, pæne abditis.
7. _Genus_--ANELASMA, _Darwin_. ('Lepadidæ,' p. 169.)
Capitulum sine valvis; aperturâ amplâ; pedunculus fimbriatus, sub-globosus, infossus.
8. _Genus_--ALCIPPE, _Hancock_. (Darwin, 'Balanidæ,' p. 529.)
(Fœm.) Capitulum sine valvis, aperturâ spinosâ; pedunculus ad basalem extremitatem crescit; superficie rostrali depressâ et disco corneo tectâ; capitulum et pedunculus in cavitate conduntur, ab ipso cirripedio formatâ.
9. _Genus_--IBLA, _Leach_. (Darwin, 'Lepadidæ,' p. 180.)
(Herm. et Fœm.) Valvæ 4, corneæ; pedunculus spinis corneis, persistentibus vestitus.
10. _Genus_--SCALPELLUM, _Leach_. (Darwin, 'Lepadidæ,' p. 215, et 'Lepad. Foss.' p. 13.)
(Herm. et Fœm.) Valvis 12 ad 15; lateribus verticilli inferioris quatuor vel sex, lineis incrementi plerumque convergentibus; sub-rostrum rarissime adest; pedunculo squamifero, rarissime nudo.
CHARACTERES VALVARUM IN SPECIEBUS FOSSILIBUS.
Carina angusta, introrsùm arcuata, ab apice ad marginem basalem paululum dilatata; carinæ parietes valde inflexi, costis manifestis a tecto plerumque disjuncti; in multis speciebus intra-parietibus instructa; intraparietes nonnunquam supernè producti ultra umbonem carinæ, qui fit inde subcentralis; carinæ parietum lineæ incrementi perobliquæ. Scuta plerumque subconvexa et tenuia, trapezoidea; marginibus tergalibus lateralibusque angulo insigni disjunctis.
11. _Genus_--POLLICIPES, _Leach_. (Darwin, 'Lepadidæ,' p. 293, et 'Lepad. Foss.' p. 42.)
Valvæ ab 18 usque ad 100 et amplius; lateribus verticilli inferioris multis; lineis incrementi deorsùm ordinatis; subrostrum semper adest; pedunculus squamiferus.
CHARACTERES VALVARUM IN SPECIEBUS FOSSILIBUS.
Carina ab apice ad marginem basalem multum dilatata, apice plerumque liberè prominente; carinæ parietes à tecto non distincté separati, lineis incrementi parietum parum obliquis. Scuta plerumque subsolida, convexa, subtrigonalia, margine tergo-laterali plus minusve eminente, sed non angulo in margines duos discreto.
12. _Genus_--LITHOTRYA, _G. B. Sowerby_. (Darwin, 'Lepadidæ,' p. 332.)
Valvæ 8, si inter eas parvum (sæpe rudimentale) rostrum et duo parva latera numerentur; incrementi lineis concinnè crenatis; pedunculus squamis calcareis parvis vestitus, in verticillis superioribus crenatis, aut calyci basali calcareo aut discorum ordini affixus.
13. _Genus_--LORICULA, _G. B. Sowerby, jun._ (Darwin, 'Lepad. Foss.' p. 81.)
Capitulo decem (fortasse) valvis instructo. Pedunculo seriebus decem squamarum lævium calcarearum instructo; sex lateralibus multum transversè elongatis; quatuor terminalibus angustis; secundùm pedunculi margines rostralem et carinalem decurrit sutura medialis recta, squamis non intersecantibus.
ORDO II. ABDOMINALIA. (Darwin, 'Balan.' p. 563.)
Cirripedia quibus carapax lageni-formis est; corpus ex 1 cephalico, 7 thoracicis, 3 abdominalibus segmentis constat; quorum abdominalia tribus cirrorum paribus muniuntur; thoracica membris carent. Oris labrum longè producitur et motus proprios efficit; œsophagi inferior extremitas dentibus munitur. Larva, primò ovöides, sine externis membris, sine oculo; postremò binocula, thoracicis cruribus nullis.
1. _Genus_--CRYPTOPHIALUS, _Darwin_. ('Balanidæ,' p. 566.)
ORDO III. APODA. (Darwin, 'Balan.' p. 587.)
Cirripedia quibus carapax ad duo separata fila (quæ defigendo inserviunt) redactus est. Corpus ex 1 cephalico, 7 thoracicis, 3 abdominalibus segmentis constat, quæ omnia cirris carent. Os suctorium, mandibuli et maxillæ (dorsis inter se appositis) cucullo includuntur, qui è labro et palpis confluentibus formatur. Metamorphoses incognitæ.
1. _Genus_--PROTEOLEPAS, _Darwin_. ('Balanidæ,' p. 589.)
SYNOPSIS
ET
INDEX SYSTEMATICUS SPECIERUM,
_Et recentium, et fossilium_.[157]
[157] In hâc portione Synopsis, Auctorum nomina referunt solummodo ad species.
ORDO I. THORACICA.
Fam. BALANIDÆ.
Sub-Fam. BALANINÆ.
[_Sectio_ †.]
1. _Genus_--BALANUS.
_Sectio_ A.
Parietes et basis et radii poris perforati.
_Sectio_ B.
Parietes et basis interdum poris perforati; radii nunquam; testæ axis rostro-carinalis elongatus; basis cymbiformis, Gorgoniis et Milleporis affixa.
_Sectio_ C.
Parietes et basis semper poris perforati; radii nunquam.
_Sectio_ D.
Parietes semper poris perforati; basis et radii nunquam.
_Sectio_ E.
Basis membranacea.
_Sectio_ F.
Parietes et radii nunquam, basis interdum, poris perforata; basis interdum admodum tenuis, adeo ut vix distingui possit.
[_Sectio_ A.]
1. _Balanus tintinnabulum_, Linn. (Darwin, 'Balanidæ,' p. 194, Tab. 1 et 2, fig. 1.)
B. testâ à roseâ ad atropurpuream variante, sæpe longitudinaliter virgatâ et costatâ. Orificio plerumque integro, interdum dentato. Scuti cristâ articulari latâ et reflexâ. Tergi margine basali plerumque in contrariis calcaris partibus rectam lineam formante.
_Hab._--In tepidis et torridis ubique maribus. _Foss._ in Europâ.
2. _Balanus tulipiformis_, Ellis. (Darwin, 'Balanidæ,' p. 204, Tab. 2, fig. 2.)
B. testâ, obscurè roseâ, interdum purpurascente; orificio dentato. Scuto externè admodum lævi membranâ tecto. Tergi musculorum depressorum cristis distinctis.
_Hab._--In Europâ meridionali et Madeirâ.
3. _Balanus psittacus_, Molina. (Darwin, 'Balanidæ,' p. 206, Tab. 2, fig. 3.)
B. testâ pallidè roseâ, sordidâ; orificio hexagonali. Scuti cristâ articulari minimâ, quæ cum adductoris cristâ, admodum prominente, confluit; musculo depressore laterali tubulari cavitate locato, quæ sursùm ad valvæ apicem extendit. Tergi apice producto, aculeato, purpureo; calcare ab angulo basi-scutali propiùs quam suâ ipsius latitudine distante.
_Hab._ et _foss._ in Americâ meridionali.
4. _Balanus Capensis_, Ellis. (Darwin, 'Balanidæ,' p. 209, Tab. 2, fig. 4.)
B. testâ colore lucidè-roseo, umbratâ et sæpe longitudinaliter virgatâ. Scuto ut in B. psittaco. Tergi apice producto aculeato, albo; calcare ab angulo basi-scutali suâ ipsius latitudine distante.
_Hab._--In Africâ meridionali.
5. _Balanus nigrescens_, Lamarck. (Darwin, 'Balanidæ,' p. 210, Tab. 2, fig. 5.)
B. testâ cinereâ, pallidè-cæruleo aut atro-cæruleo, aut albo tinctâ. Scuti cristâ articulari parvâ, deorsùm in parvum, acutum aculeum desinente; adductoris cristâ prominente. Tergi apice producto, aculeato.
_Hab._--In Australiâ.
6. _Balanus decorus_, Darwin. ('Balanidæ,' p. 212, Tab. 2, fig. 6.)
B. parietibus pallidè-roseis: radiis aliquanto intensioribus. Scuti cristâ articulari parvâ. Tergi sulco longitudinali admodum tenui et aperto; marginibus basalibus utrinque ad calcar declivibus.
_Hab._--In Novâ Zealandiâ.
7. _Balanus vinaceus_, Darwin. ('Balanidæ,' p. 213, Tab. 2, fig. 7.)
B. testâ fusco-purpureâ; parietum laminâ interiore cancellatâ. Scuto longitudinaliter et tenuiter striato. Tergi sulco longitudinali tenui et aperto: marginibus basalibus utrinque ad calcar declivibus.
_Hab._--In occidentali littore Americæ merid.
8. _Balanus Ajax_, Darwin. ('Balanidæ,' p. 214, Tab. 3, fig. 1.)
B. testâ globoso-conicâ, sæpe in axe rostro-carinali elongatâ, pallidè-roseâ, lævi, admodum crassâ: tubis parietalibus prope marginem basalem, cylindricis et minimis. Scuti cristâ articulari latâ, reflexâ.
_Hab._--In Arch. Philippino.
[_Sectio_ B.]
9. _Balanus stultus_, Darwin. ('Balanidæ,' p. 216, Tab. 3, fig. 2.)
B. parietibus et basi porosis: testâ albâ aut purpurâ leviter tinctâ. Scuti margine basali in medio prominente. Tergi sulco longitudinali supernè clauso; calcare angulo basi-scutali non approximato.
_Hab._--In Indiâ occident. et orient.
10. _Balanus calceolus_, Pallas. (Darwin, 'Balanidæ,' p. 218, Tab. 3, fig. 3.)
B. parietibus et basi porosis. Scuto musculi depressoris lateralis fossâ parvâ, profundâ.
_Hab._--In Africâ occidentali et Indiâ. _Foss._ in Angliâ.
11. _Balanus galeatus_, Linn. (Darwin, 'Balanidæ,' p. 220, Tab. 3, fig. 4.)
B. parietibus non porosis: basi porosa. Tergi apice, propter cristæ articularis magnitudinem, quadrato.
_Hab._--In Americâ sept. et Indiâ occident.
12. _Balanus cymbiformis_, Darwin. ('Balanidæ,' p. 221, Tab. 3, fig. 5.)
B. parietibus et basi non porosis. Scuti et tergi cristis articularibus minimis. Tergo lato, pæne æquilaterali.
_Hab._--In Indiâ.
13. _Balanus navicula_, Darwin. ('Balanidæ,' p. 221, Tab. 3, fig. 6.)
B. parietibus et basi non porosis: valvis testæ carino-lateralibus admodùm angustis, latitudine à vertice ad imum pæne æquâ. Radiorum marginibus suturalibus lævibus. Scuto externè longitudinaliter striato.
_Hab._--In Indiâ.
[_Sectio_ C.]
14. _Balanus trigonus_, Darwin. ('Balanidæ,' p. 223, Tab. 3, fig. 7.)
B. parietibus costatis, purpureo-rubris, maculatis: orificio lato, trigonali, vix dentato. Scuto crasso, fossularum seriebus longitudinalibus 1 ad 6. Tergo sine sulco longitudinali; calcare truncato ad plenùm 1/3 valvæ latitudine.
_Hab._--In Arch. Indiæ Orient.: Australiâ: Californiâ: Peruviâ.
15. _Balanus spongicola_, Brown. (Darwin, 'Balanidæ,' p. 225, Tab. 4, fig. 1.)
B. parietibus plerumque lævibus, interdum longitudinaliter plicatis; roseis; orificio dentato: scuto longitudinaliter striato: tergum, apice producto, sine sulco longitudinali; calcare truncato 1/3 valvæ latitudine.
_Hab._--In Europâ meridionali et mediâ, Africâ meridionali; _var._ in Indiâ occidentali. _Foss._ in Angliâ, in "Miocenâ Formatione."
16. _Balanus lævis_, Bruguière. (Darwin, 'Balanidæ,' p. 227, fig. 2.)