Part 19

Balanus tintinnabulum north and south of the equator (1 to 5). psittacus* south. vinaceus* " trigonus north and south (4 and 5). lævis* " concavus " (4 and 5). pœcilus* south. improvisus south (and north?) (1). nubilus* north. glandula north, and Southern Pacific Ocean. cariosus* north. Tetraclita porosa north and south (4 and 5 and W. Indies). Elminius Kingii* south. Chthamalus stellatus north. cirratus* south. scabrosus* " fissus* north and south. Hembeli* north. Verruca lævigata* south. Pollicipes elegans* south and north. polymerus* " Cryptophialus minutus* south.

Here we have on this long line of coast, 22 species, of which 15 are peculiar.

(4.) THIRD PROVINCE: _Indian Archipelago (including the Philippines, Malacca, Borneo, Sumatra, Java, and New Guinea, and eastern coast of India)._

Balanus tintinnabulum (1 to 5). Ajax* navicula* stultus and West Indies. trigonus (3 and 5). concavus (3 and 5). amphitrite (1 to 5). patellaris* amaryllis (5). quadrivittatus* Acasta lævigata and Red Sea. fenestrata* purpurata* sporillus* Tetraclita porosa (3 and 5) and West Indies. costata* vitiata (5). cœrulescens Pacific Ocean. radiata (5) and West Indies. Pyrgoma cancellatum* grande* milleporæ* crenatum* monticulariæ* Creusia spinulosa and West Indies. Chthamalus stellatus (1 and 3). intertextus* Chamæsipho scutelliformis* Octomeris brunnea Pœcilasma fissa* eburnea* Dichelaspis Warwickii* Ibla Cumingii* Scalpellum rostratum* Pollicipes mitella* Lithotrya Nicobarica* truncata and Pacific Ocean.

Here we have 37 species, of which 24 are peculiar to this province.

(5.) FOURTH PROVINCE: _Australia (including New Zealand)._

Balanus tintinnabulum (1 to 5). nigrescens* decorus* trigonus (3 and 4). concavus (3 and 4). amphitrite (1 to 5). amaryllis (4). allium* vestitus* imperator* Acasta sulcata* glans* Tetraclita porosa (3 and 4). rosea (2). purpurascens* vitiata (4). radiata (4) and West Indies. Elminius plicatus* simplex* modestus* Chthamalus antennatus* Chamæsipho columna* and Pacific Ocean (?). Pachylasma aurantiacum* Catophragmus polymerus* Alepas tubulosa* Ibla quadrivalvis* Scalpellum Peronii* Pollicipes spinosus* sertus* Lithotrya cauta*

Here we have 30 species, of which 21 are peculiar.

_Geological History._

The ancient history of the Balanidæ is a brief one. No secondary species has hitherto been discovered; in my monograph on the fossil Lepadidæ[80] I have shown that the negative evidence in this case is of considerable value, and consequently that there is much reason to doubt whether any member of the family did exist before the Eocene period. The existence of a Cretaceous Verruca is an apparent exception to the rule, as this genus has hitherto always been ranked amongst sessile cirripedes; but Verruca, as we now know, must be placed in a family by itself, quite distinct from the Balanidæ. Balanus is the oldest genus as yet known; it first appeared in Europe and North America, during the deposition of the eocene beds; and was at that time, as far as our information at present serves, represented by very few species. In South America, one species of Balanus abounds in individuals in the ancient Patagonian tertiary formation. I have seen, in the British Museum, specimens, said to have come from the eocene nummulitic beds near the mouth of the Indus, belonging to the second section of the genus. Generally, the extinct forms belong to the last section of this genus, which has the parietes not permeated by pores. During the miocene and pliocene ages, sessile cirripedes abounded. No extinct genus in this family has hitherto been discovered. It is singular, that though the Chthamalinæ approach much more closely than do the Balaninæ to the ancient Lepadidæ, of which so many species have been found fossil even in the older Secondary formations, yet that only one species of one genus of this sub-family has been hitherto found in any deposit; and that species is the still existing _Pachylasma giganteum_, in the modern beds of Sicily. During the epoch of the Glacial deposits in Scandinavia, Scotland, and Canada, the still existing species seem to have abounded; and they attained larger average dimensions than the same species now do on the shores of Great Britain, or even on the shores of the northern United States, where the average size seems larger than on this side of the Atlantic.

[80] Since the note to page 5 of that work was written, I have been informed that the so-called cretaceous _Tubicinella maxima_ is not a Cirripede.

Under the genus Balanus, I have given my reasons for never naming species in this large and difficult genus, without examining the opercular valves: it has been owing to this, as it appears to me, proper want of caution, that there are so many nominal species. Thus it is made to appear in catalogues, that the tertiary seas abounded with species of Balanus to an extent now quite unparalleled in any quarter of the world. Bronn,[81] for instance, in his invaluable 'Index Palæontologicus,' gives the names of 35 Balani, found fossil in Europe, and I have not counted those found only in alluvial deposits, as they would certainly be the same as the still living species. Now I know only 11 recent Balani on the shores of all Europe, from the North Pole to lat. 30°; and of these I doubt whether _B. balanoides_ and _improvisus_ have been found fossil. In the Red Crag there is one extinct Balanus: in the Coralline Crag, which seems to have been very favorable to the existence of Cirripedes, there are six species of Balani, of which two are absolutely extinct, and one does not occur in any neighbouring sea: in the Eocene formations the species seem to have been rare, and I have seen only one, and that is an extinct form. Taking these several facts into consideration, and bearing in mind that Cirripedes usually range widely, I do not believe, if all the specimens of Balani hitherto found in the several tertiary formations, from the eocene to the glacial deposits, throughout Europe, were collected together, they would amount to 20 species. I have myself seen, in a recognisable state, only 12 fossil species, of which five are extinct, or not found in any neighbouring sea: I think it probable that three other recent species, viz. _B. tulipiformis_, _perforatus_, and _amphitrite_, may occur in the Mediterranean formations; and this would make 15 species. Therefore in the above estimate of 20 species, five are allowed for species existing in European collections, but not hitherto seen by me; and this, I believe, is a very full allowance. Consequently, even on the supposition that the five species just admitted as possibly existing in cabinets, and that the other five extinct species, which I have seen and examined, have all been previously named by other authors, a supposition excessively improbable, even then there would be 15 superfluous names in Bronn.

[81] To save any other person, interested in fossil Cirripedia, going through the several works quoted by Bronn, I have given some remarks on his list of species, in an appendix at the end of the Balanidæ.

The following short table shows how Cirripedes, including all three Families, were represented in Great Britain, throughout the several TERTIARY STAGES.

A = Living species but found fossil in some tertiary deposit. B = Mammilliferous crag, and glacial deposits. C = Red crag. D = Coralline crag. E = Eocene.

+----------------------------+---+---+---+---+---+ | Name. | A | B | C | D | E | +----------------------------+---+---+---+---+---+ | Balanus tintinnabulum | * | | * | | | | calceolus | * | | | * | | | spongicola | * | | | * | | | concavus | * | | * | * | | | porcatus | * | * | * | | | | crenatus | * | * | * | * | | | Hameri | * | * | * | | | | bisulcatus | | | * | * | | | dolosus | | * | | | | | inclusus | | | | * | | | unguiformis | | | | | * | | Acasta undulata | | | | * | | | Pyrgoma anglicum | * | | | * | | | Coronula barbara | | | * | | | | Verruca Strömia | * | * | * | * | | | Scalpellum magnum | | | | * | | | quadratum | | | | | * | | Pollicipes reflexus | | | | | * | +----------------------------+---+---+---+---+---+ | Total, 18, recent and } | | | | | | | extinct, found fossil in } | 9 | 5 | 8 |10 | 3 | | Great Britain, in some } | | | | | | | tertiary deposit } | | | | | | +----------------------------+---+---+---+---+---+

As affording some standard of comparison by which to compare the number of fossil species, at any period, in relation to the number of species probably existing in the neighbouring seas during the same epoch, I may state that there are now living and propagating on the shores of Great Britain, 18 species belonging to the three Families included in the above table. I have not counted three species, in the genera Alcippe and Conchoderma, which, from the minuteness of their valves, it is hardly possible would be found fossil. On the other hand, I have included in the 18, five species of Lepas, which from floating and being oceanic, are more likely to be cast up on beaches, than to be imbedded in sedimentary deposits; so that 13 would, perhaps, be a safer number, as a standard of comparison. Now in the coralline crag, which seems to have been eminently favorable for the existence and subsequent preservation of Cirripedes, and which has been so well worked, only nine fossil species, as may be seen in the table, have been as yet discovered.

Sub-Family--BALANINÆ.

_Shell with the rostrum having radii, but without alæ; lateral compartments all having alæ on one side and radii on the other side; parietes generally either porose, or longitudinally ribbed on their inner surfaces._

_Mouth with the labrum notched in the middle, not swollen; palpi large, almost touching each other; mandibles generally with the lower teeth laterally double; third pair of cirri with their segments resembling those of the second pair._

_First Section._†

_Scutum and tergum articulated together, or overlapping each other; each branchia composed of a single plicated fold._

_Genera_--Balanus; Acasta; Elminius; Tetraclita; Pyrgoma; Creusia; Chelonobia.

_Second Section._††

_Scutum and tergum (when both are present) not overlapping each other; basis membranous; parietes often deeply folded, with the outer lamina, towards the basis, generally imperfect; each branchia composed of two plicated folds; shell attached to living vertebrata._

_Genera_--Coronula; Platylepas; Tubicinella; Xenobalanus.[82]

[82] At the end of the volume a Synopsis is given, which will serve as a systematic index for the discovery of generic and specific names.

The Balanidæ may be divided into two sub-families; namely, the Balaninæ and Chthamalinæ; and, in the former, the genera, as we see, may be very naturally grouped into two sections. The Balaninæ differ from the Chthamalinæ, as far as the shell is concerned, in the rostrum having radii but no alæ, all the lateral compartments having both radii and alæ; on the other hand, in the Chthamalinæ, the rostrum has alæ, and the rostro-lateral compartments radii on both sides, and therefore no alæ. These differences probably arise, as already explained, from the perfect confluence, in the Balaninæ, of the true rostrum with the rostro-lateral compartments. In Chelonobia, belonging to the Balaninæ, we see an intermediate state, with the fusion not quite effected: on the other hand, in one genus amongst the Chthamalinæ, namely, Pachylasma, we must look to the shell at a very early age, to find the rostrum with its alæ, distinct from the rostro-lateral compartments. In Tetraclita, Elminius, and Creusia, the carino-lateral compartments are aborted, or possibly confluent with the lateral compartments, making altogether only four: in Pyrgoma all the compartments are fused together and form a solid ring. The sub-genus Acasta is, in one sense, very natural, as it includes species most closely allied: in another sense it is far from natural, as some of the species can hardly be distinguished from those species of Balanus, which live attached to Gorgoniæ: I almost regret I did not merge the species of Acasta into Balanus. In the Balaninæ generally the parietes are either porose, or are furnished on their internal surfaces with regular ribs, representing the longitudinal parietal septa, which in other species form the tubes or pores; there are, however, many exceptions to this rule in several species of Balanus, in Acasta and Elminius, all of which have the parietes of their shells internally quite smooth, or only irregularly roughened with points.

Looking to the animal's body, in the Balaninæ, the labrum is always notched in the middle, and is never swollen or bullate, for the outer and inner folds of membrane of which it is composed lie close together. The palpi are large, so that their tips almost touch each other. The mandibles, generally, have their lower main teeth laterally double. Of the cirri, the third pair invariably much more closely resembles, in its whole structure, and in its action, the second than the fourth pairs; and it is also generally separated by a small interval from the fourth pair.

I have already under the Family sufficiently entered on the relations of the Balaninæ to the Chthamalinæ, and of the genera, one to the other, so that I need not here add anything.

I can point out no difference in habits or geographical distribution between the Balaninæ and Chthamalinæ.

1. _Genus_--BALANUS, Auct.[83]

[83] The name Balanus was used, almost as at present, by Lister and Hill, before the introduction of the binomial system. Since that period the first two authors, as far as I know, who used this name, were Da Costa, in his 'Hist. Nat. Test. Brit.,' in 1778; and Bock, in the 'Naturforscher,' for the same year; Bock, however, applied it to a Chelonobia.

CONOPEA (pars generis). _Say._ Journal Nat. Sc. Philadelphia, vol. ii, part ii, 1822.

MESSULA (do.). _Leach._ Zoological Journal, vol. ii, 1825.

CHIRONA (do.). _J. E. Gray._ Philosoph. Transacts., 1835, p. 37.

_Compartments six; basis calcareous or membranous; opercular valves sub-triangular._

_Distribution._--Mundane: in the warmer seas.

_General appearance._--The shape of the shell in the different species varies from depressed conical to cylindrical; the latter form being generally assumed when specimens are crowded together; but some species, as _B. balanoides_, _crenatus_, and _lævis_, seem more subject than others to be thus affected. The colour is either white, generally tinted by the yellowish or brownish epidermis, or any colour intermediate between bright pink and rich blue, purple being the prevailing tint. The persistence of the so-called epidermis is very different in different species, being even sometimes highly variable in the same species. The surface is either smooth or more commonly folded longitudinally, or sharply ribbed. The orifice differs in form from diamond-shape to trigonal; the carinal end, owing to the shape of the carina, being always sharper or narrower than the rostral end. The size of the orifice, in proportion to the shell, varies accordingly as the latter is more or less conical or cylindrical. The orifice is either entire or more or less deeply toothed, in proportion to the degree of obliquity of the summits of the radii and alæ. The radii almost always have smoother surfaces than the parietes. In some few species the radii are not developed, the sutures being marked only by fissure-like lines; in others they are very narrow, and in this case their upper margins are generally rounded and smooth, instead of being straight and jagged. The carino-lateral compartments are usually much narrower than the lateral compartments, occasionally in an extreme degree, as in _B. allium_. The shell is generally strong, sometimes to a wonderful degree; but the strength and thickness vary in the individuals of some of the species. By the action of hot caustic potash, the compartments in several species, such as _B. Hameri_ and _crenatus_, separate on a touch; in others, they adhere so strongly as to prove that the sutures must be calcified together. In this genus we have the largest known sessile cirripede, viz., the _B. psittacus_, and on the other hand many small species; but it is very difficult, except in well-known species, to ascertain the average or even the maximum dimensions.

_Scutum._--This valve is almost triangular, with the basi-tergal corner more or less rounded off. The prominent lines of growth are sometimes crossed by longitudinal striæ. Internally, the articular ridge projects to a very different degree in the different species; its lower end is sometimes (as in _B. lævis_, Pl. 4, fig. 2 _c_) produced downwards as a small, sharp, free style; there is always an articular furrow receiving the inflected margin of the tergum. There is always an impression left by the attachment of the adductor scutorum muscle; and often its lower side is bounded more or less closely by a sharp adductor ridge, running some way down the valve; this ridge is occasionally almost confluent, in its upper part, with the articular ridge, and in this case sometimes it forms, together with the inflected tergal margin, a large tubular cavity, running up, as in _B. psittacus_ (Pl. 2, fig. 3 _c_), almost to the apex of the valve. Almost invariably there is a slight pit or depression for the lateral depressor muscle; sometimes within the depression there is a little ridge, as in _B. perforatus_ and _nubilus_ (Pl. 4, fig. 3 _a_, and Pl. 6, fig. 2 _a_); and in the case of _B. vestitus_, _flosculus_, and _imperator_ (Pl. 8, figs. 3 _a_, 4 _a_), there are regular crests for this same purpose. The rostral depressor muscle is usually attached in a small pit formed by the folding over of the lower part of the occludent margin: in _B. imperator_ (Pl. 8, fig. 4 _a_) there are regular crests for its attachment, and traces of them may be discovered in _B. vestitus_.

_Tergum._--This valve is more nearly triangular than any other shape, with the spur more or less prominent. The apex generally projects a little above the level of the scutum; in some species it consists of a triangular and solid, in others (Pl. 2, fig. 3 _b_) of an almost cylindrical, extremely sharp, inwardly curved, and very prominent beak. This beak is generally purple; it is sometimes hollow, and occupied by a thread of corium. Its formation, and the apparent sliding up of the whole tergum, so as to project above the scutum, has been described under the family. From an account given to me by a person who kept _B. porcatus_ alive, the beaks appear to be used, when the operculum is touched, as an organ of defence,--the animal striking with them. The tergal margin is more or less inflected; and the carinal margin is convex in different degrees, and, in some species, is added to by upturned zones of growth. The basal margin either forms a nearly straight line on opposite sides of the spur, or more commonly slopes towards it in various manners. The spur, or basal projection, is rarely placed in the middle of the basal margin, generally near, sometimes close to the basi-scutal angle; it varies much in length and breadth, and is sometimes even half the width of the valve. The surface of the valve is almost always more or less depressed, sometimes so much as to form a deepish furrow, the "longitudinal furrow," which extends from the apex to the extremity of the spur. When the furrow is deep, its sides, as the specimen grows old, almost always become folded inwards, so as to touch, and then the furrow becomes converted into a closed fissure: in this latter case the folded sides generally form a central crest on the spur. Internally, in the middle of the upper part of the valve, the articular ridge is more or less prominent, forming the carinal margin of the articular furrow, in which the articular ridge of the scutum is lodged; occasionally, however, this articular ridge can hardly be said to exist. In most species the tergal depressor muscle is attached to sharp crests on the basi-carinal corner of the valve, but these are almost obliterated in other species.