Part 73

Fig. 1 _a_, Chthamalus intertextus, shell; 1 _b_, scutum and tergum, calcified together, with the suture obliterated in the upper part, internal view of. 2 _a_, Chthamalus scabrosus, shell; 2 _b_, scutum, internal view of; 2 _c_, tergum, internal view, _p_, plate forming one side of the cavity in which the depressor muscle is attached; 2 _d_, tergum, as seen from almost vertically beneath; _p_, pit for the depressor muscle; _q_, special pit for the lateral, properly scutal depressor muscle; _r_, articular furrow. 3 _a_, Chamæsipho columna, shell; A, rostrum; B, lateral compartment, probably formed by fusion of the rostro-lateral and lateral compartments; _E_, carina; 3 _b_, 3 _c_ scutum and tergum, internal views of. 4 _a_, Chamæsipho scutelliformis, shell much enlarged, seen from above; A, rostrum, separated by imperfect sutures from the (B) lateral compartments, which are formed probably by the fusion of the rostro-lateral and lateral compartments; E, carina; B stands opposite one of the inward folds of the wall, leading into one of the tubular apertures, which runs (generally with an irregular spiral curve) through the whole thickness of the shell down to the surface of attachment. The carina has two of these apertures. 4 _b_, Chamæsipho scutelliformis, another specimen, seen from the under side, letters of reference the same. 4 _c_, Chamæsipho scutelliformis, rostrum, disarticulated, enlarged, showing the alæ. 4 _d_, Chamæsipho scutelliformis, scutum and tergum, internal views of. 5 _a_, Pachylasma giganteum; 5 _b_, rostrum of an extremely young specimen, much enlarged, showing its compounded nature, viz., of a true rostrum and rostro-lateral compartments; 5 _c_, scutum and tergum, external views of; 5 _d_, scutum and tergum, internal views of.

PLATE 20.

_Genera_--PACHYLASMA, OCTOMERIS, AND CATOPHRAGMUS.

Fig. 1 _a_, Pachylasma aurantiacum, shell, lateral view; A, rostrum, separated only by the finest suture from B, the rostro-lateral compartment, which latter has a mere rim-like radius on the side facing the lateral (C) compartment. The latter (C) has a great ala, and is separated from the (D) carino-lateral compartment, by the finest suture; D has a rim-like radius; E, carina, with very large alæ (_a_). 1 _b_, Pachylasma aurantiacum, inside view of about half the shell, showing the compound rostrum, consisting of the true rostrum (A) and the two rostro-lateral (B, B) compartments; of the latter, that to the left has a shoulder, receiving the ala of the lateral compartment which has been removed; the ala of the lateral compartment extends, in the upper part, over the whole width of the rostro-lateral compartment, as may be seen on the right-hand, B; C, lateral compartment; D, carino-lateral compartment, with a shoulder (_b_) to receive the ala of the carina, which has been removed. 1 _c_, 1 _d_, Pachylasma aurantiacum, scutum and tergum, external views of. 2 _a_, Octomeris angulosa, shell seen from above; 2 _b_, scutum and tergum, internal views of. 3 _a_, Octomeris brunnea, shell seen from above; 3 _b_, scutum and tergum, external views of. 4 _a_, Catophragmus polymerus, shell seen from above. 4 _b_, " " external view of one of the scales or valves, from the second whorl, counting from the inside. 4 _c_, " " outline of the basal edges of all the valves of a shell; A, rostrum; B, rostro-lateral; C, lateral; D, carino-lateral compartments; E, carina. 4 _d_, " " external view of a portion of the shell of a much corroded and worn down specimen, serving almost as a transverse section; C, lateral compartment, D, carino-lateral compartment. 4 _e_, " " scutum and tergum, internal views of.

PLATE 21.

_Genus_--VERRUCA.

N.B.--_Letters of reference the same throughout the Plate._

A, rostrum. B, carina. S, moveable scutum, S′, scutum fixed and modified so as to form part of the shell. T, moveable tergum, T′, tergum fixed and modified so as to form part of the shell. In S, and S′, _a_ is the occludent margin; _b_, the basal margin; _m_, the plate to which the adductor muscle is fixed; _o_, a ledge formed during continued growth, in the upper part of the fixed scutum, in order to keep the orifice perfectly closed; this ledge is seen distinctly only in fig. 5. In S and S′ the tergal margin is marked by small dashes; (′) being the upper articular ridge, and (′′), the second or lower articular ridge: in S′ (′′) is called the parietal portion of the valve. In T and T′, the scutal margin is marked by small dashes; (′) being the first and upper articular ridge, hardly distinct from the occludent margin, and called in T′′ the occludent rim; (′′) is the second or middle, and (′′′) the lower or third articular ridge, called in T′′ the parietal portion of the valve; _x_ is the carinal margin, called in T′ the carinal rim, and _z_ the basal margin; _o_ is the occludent margin: in T′, a ledge is formed across the under side close to the apex, which ledge is necessary to keep the orifice neatly closed, owing to the apex of the moveable tergum coming to project freely during growth.

Fig. 1 _a_, Verruca Strömia, specimen with the left hand scutum and tergum fixed and modified into part of the shell. 1 _b_, Verruca Strömia, (with left hand scutum and tergum fixed), with the valves and compartments separated from each other; the homologous parts of the opercular valves are marked by corresponding letters and dashes. 1 _c_, Verruca Strömia, left hand scutum and tergum fixed, viewed from the under side. 1 _d_, Verruca Strömia, _smooth var._, reversed specimen, _i. e._, with the right hand scutum and tergum fixed and modified into part of the shell. 1 _e_, Verruca Strömia, shell seen from the under side; the right hand scutum and tergum (as in 1 _d_) being the fixed pair: the moveable scutum and tergum (S, T) are seen in the shade at the bottom of the shell, and their shape will be best understood by looking at fig. 1 _f_. The fixed scutum and tergum S′, T′, differ a little in shape, and in the form of their line of junction, from the same two valves (reversed) in fig. 1 _c_. 1 _f_, Verruca Strömia, moveable scutum and tergum, seen from the under side, taken from a specimen, in which (as in 1 _d_ and _e_) the right hand scutum and tergum were the fixed pair. 2, Verruca Spengleri, scutum seen from the under side, showing the medial, prominent adductor ridge; taken from a specimen, in which the right hand scutum and tergum were fixed. 3 _a_, Verruca lævigata, scutum and tergum, external view of, from a specimen in which the left hand pair was fixed; 3 _b_, scutum and tergum, internal view of, from a specimen, in which the right hand pair was fixed. 4, Verruca prisca, scutum and tergum, external view of, from a specimen, in which left hand pair was fixed. 5, Verruca nexa, with the valves separated, the left hand scutum and tergum being the fixed and modified pair. 6, Portion of ribbed shell of a Venus, to which a _Verruca Spengleri_ had been attached, showing the peculiar form of the excavation.

PLATE 22.

ALCIPPE LAMPAS.

Fig. 1, Entire animal (female and two males) greatly magnified, being an unusually symmetrical specimen, partly copied from Mr. Hancock's Plate ('Annal. and Mag. Nat. Hist.' ser. 2, vol. 4, Pl. VIII). H, horny disc and surface of attachment; _a_, projection formed by the lower end of the lip of the orifice leading into the sack; _m_, a pair of males, of their proper proportional sizes, attached in their ordinary position. 2, Entire animal, much distorted. 3, Small portion of a Fusus (copied from Mr. Hancock's Plate), perforated by the Alcippe; the darker curved marks are the slit-like orifices, leading into the chambers; the latter are seen from the outside, owing to a difference of tint in the shell of the mollusc where worn thin over the chambers; they are represented by the fan-shaped shaded patches. 4, One of the orifices, leading into a chamber, much enlarged; _a_, the curved narrow end, which was open and used when the animal was young, but has since been closed externally by sand or shelly matter, and internally by the upward prolongation of the horny disc; _b_, rims of an inorganic, calcareous deposit, by which the narrow end of the orifice is kept of the due degree of narrowness. 5, Longitudinal section through the outer envelopes of a very symmetrical specimen, giving a lateral view of the included body. _a_, point at the lower end of the orifice of the capitulum, leading into the sack. _b_, end of adductor muscle. _c_, mass of branching ovarian cæca, much developed and protuberant on the under side. _d_, basal point of the quasi-peduncle, projecting beyond the level of the horny disc (H, H). _e_, sack or open cavity: of the two branchiæ or ovigerous fræna, one has been removed with the outer envelopes, the other is hidden by the projection caused by the medial distended mass of the ovarian cæca. _e′_, lateral line of junction of the body to the outer envelopes; which latter have been here cut through in removing the near half of the capitulum and peduncle. _f_, notch separating the capitulum or upper part from the peduncle or lower part of the external covering: this notch varies much in depth. _g_, the end (homologically the carinal end), of the orifice leading into the sack, where the cutting of the outer envelopes has commenced. H H, horny disc, cut longitudinally down the middle. _h_, first pair of cirri. _i_, prosoma (homologically the second thoracic segment). _k_, the thoracic segment, which would have borne the second pair of cirri, had such existed. _l_, thoracic segment, which should have borne the third pair. _m_, thoracic segment, which should have borne the fourth pair. _n_, thoracic segment, very small, bearing the fifth pair of cirri. _n′_, fifth pair of cirri, only one cirrus on the near side being represented. _o′_, sixth cirrus, borne on the last thoracic segment, too small to be shown. _p_, caudal appendages. 6, one side or lip of the orifice leading into the sack, greatly enlarged, seen on the inner side, formed of an inner membrane, _b_, (on which the long hairs and an S-like band of spines, too fine to be plainly represented, are placed), and an outer membrane _c_, studded with short, thick spines, the corium between these two membranes having been removed; _a_, projection at lower end of orifice; _g_, upper end of orifice, showing the point where the corresponding side or lip of the orifice has been cut away. 7, small portion of the external membrane, showing the star-shaped, hard, projecting points of chitine; but they are here placed too closely together. 8, front view of mouth, greatly enlarged, and with the gnathites rather unnaturally separated from each other; _h_, the first pair of cirri; in front, the outer maxillæ appear like a bilobed lower lip; the inner maxillæ (with their singular membranous swelling behind, see fig. 15), can be distinguished by their long apodemes or horny imbedded bars; behind are seen the one-toothed mandibles, with a swelling behind, probably representing the palpi; all above the mandibles consists of the immensely developed labrum, with the foreshortened ends of the row of long hairs on each side; the fold, or articulation, separating the mouth and body, is seen crossing above the basal ends of the apodemes of the maxillæ. 9, Lateral view of the coriaceous button or cushion, _c′_, on one corner of the upper segment, _b_, of the pedicel of the sixth cirrus; _c_, being the lower part of the lower segment of the one ramus of this same cirrus: the hooked hairs are rather distorted. 10, The same, viewed from the inner side. 11, Lateral view of the labrum, with the mandible, _m_, attached to it, which latter, from overhanging the œsophagus, shows the position of the mouth; _h h_, is the first cirrus on the near side; _b_, is the medial crest of labrum, on the side of which extends a long row of hairs; _a a a_, delicate membrane of side of body, attached to the margins of the labrum. 12, Diagram showing the probable manner in which the young Alcippe bores into the shell of molluscs; _a_, pupa attached by the antennæ to the outer surface of shell; _b_, outline of young Alcippe soon after its metamorphosis; the anterior or lower end has increased considerably in length, so as to project beyond the point whence the antennæ rise, and it has now penetrated the shell, being attached to the roof of its incipient chamber by its horny disc, represented by a thick black line; _c_, is the Alcippe after further growth, when it has succeeded in burying itself; the horny disc is now attached parallel to the surface of the shell; the horny disc of its former state, now lines the narrow end of the slit-like orifice leading into the shelly chamber: the above changes in position are supposed to have been effected quite gradually. The diagram, _c_, I may add, represents the position of the Alcippe for the rest of its life, the chamber being added to at both ends, sides, and bottom. 13, Lateral view of the posterior extremity of the thorax, much enlarged, with its articulated appendages represented only on one side; the four thoracic segments, _l_, _m_, _n_, _o_, correspond with those represented in fig. 5. In one monstrous specimen, segment _n_, bore a single cirrus. The posterior thoracic segment, _o_, bearing the sixth pair of cirri, _o′_, is very small and obscure, and can be seen only by separating the fifth and sixth pairs of cirri; or by longitudinally bisecting the thorax, and viewing the inner side; _n′_, fifth cirrus; _a_, lower segment, _b_, upper segment of pedicel; _c_, lower, and _d_, upper segment of the one ramus, the other ramus being represented by the coriaceous boss _c′_; _o′_, sixth cirrus, with similar segments; _p_, caudal appendage. 14, First cirrus. 15, Maxillæ, with the lower end of the apodeme cut off, showing the curious membranous swelling on the side towards the mandible.

PLATE 23.

_Genera_--ALCIPPE AND CRYPTOPHIALUS.

ALCIPPE LAMPAS.

Fig. 16, Pupa of male Alcippe lampas, viewed laterally; _a_, antennæ, _c′_, eyes attached to the apodemes; above these the single eye of the mature male may be distinguished. 17, Abdomen of the same; _p_, posterior end of thorax; _q_, abdomen; _r_, caudal appendages. 18, Male of Alcippe lampas immediately after the metamorphosis, the ventral surface being uppermost, but the specimen has been in some way distorted, as the lobe (_i_) ought to project on the opposite side; _a_, antennæ of the pupa; _g_, _h_, lateral lobes; internal organs not yet formed; orifice at upper end (_i_) not visible; scale same as for the pupa, fig. 16. 19, Male of Alcippe lampas, when fully mature; scale same as in last figure (18) and as in fig. 16. _a_, antennæ of pupa. _b_, vesicula seminalis. _c_, _eye_, (seen in fig. 16 above the eyes of the pupa, _c′_.) _d_, testis. _e_, lower transverse muscle. _f_, upper transverse muscle. _g_, _h_, lateral lobes of the external covering, answering to the sides of the peduncle of the female. _i_, terminal lobe on the ventral side of the orifice, probably corresponding with _a_ in fig. 1, Pl. 22. _k_, orifice of the tubular sack. _l_, oblique muscles on the ventral side of the sack. _m_, probosciformed penis, shown exserted; _m′_ portion within the tubular sack.

CRYPTOPHIALUS MINUTUS.

Fig. 1, Cryptophialus minutus (female with an attached male) viewed laterally, but with the disc (H) rather turned towards the beholder, much enlarged; _a_, orifice leading into the sack; H, thin horny disc by which the animal is attached within its cavity; H′, upper free worn edge of the disc; _z_, male attached in its usual position to the edge of the disc of the female. 2, Cryptophialus minutus, natural size, within a half-inch circle; this represents the largest specimen which I have ever seen. 3, Half the orifice, with a large portion of the external membrane and of the membrane lining the sack. _a_, _a_, dentated horny rim of orifice. _b_, _b_, external membrane, with the underlying corium or true skin removed. _b′_, a horny bar, expanding at its lower end into a toothed plate, and at the upper end connected with the horny rim round the orifice. _c_, _c_, membrane lining the sack. _c′_, horny bar by which this membrane is strengthened. _c′′_, thickened membrane, or bar, expanding into fibrous sheets for the attachment of a muscle. _d_, delicate lateral lip, within the outer dentated horny rim. 4, Orifice of sack, cut off, widely open, viewed from above; _a_, horny dentated rim; _b′_, top of horny bar, where united to the rim; _d_, inner lateral lip folded backward; _d′_, lip, with coarser hairs, at the carinal end of the orifice. 5, Animal with the outer tunics removed, viewed laterally. _a_, dentated horny rim of orifice, continuous with _b_, outer membrane, here cut off. _c_, inner membrane of sack, continuous with _c_, _c_, the reflexed membrane of the body, by which the body is united to the disc and outer envelopes. _e_, lancet-shaped labrum. _e′_, projection behind the labrum. _f_, palpi. _g_, outer maxillæ, between which and the palpi lie the inner maxillæ and mandibles; these latter are rather exaggerated in size. _h_, first maxilliped, in a rudimentary condition, close above which is the articulation separating the whole mouth (_o_) from the first (^1) segment of the body. _i_, _k_, tapering appendages springing from the second and third segments of the body. _l_, pedicels of the three pairs of abdominal cirri. _m_, cirri, three pairs of. _o_, mouth, of great size, formed by the confluence of the lower segments of the gnathites. ^1, first segment of body, homologically the last or seventh cephalic segment. ^2, second segment of body, homologically the first thoracic segment. ^3, third segment of body, homologically the second thoracic segment. ^4, fourth segment of body, homologically the third thoracic segment. ^5, fifth segment of body, homologically the fourth thoracic segment. ^6, sixth segment of body, homologically the fifth thoracic segment. ^7, seventh segment of body, homologically the sixth thoracic segment. ^8, eighth segment of the body, homologically the seventh thoracic segment. 6, Front of mouth; _g_, outer maxillæ; _g′_, an articulation separating the mouth from the membrane of the first segment of the body; _h_, first pair of maxillipeds; whole figure on same scale with the labrum, fig. 9. 7, Maxillæ, drawn on thrice the scale as the outer maxillæ; _a_, apodeme. 8, Mandibles, drawn on thrice the scale as the outer maxillæ. 9, Labrum, on same scale with the outer maxillæ, fig. 6, and one third of the scale of the mandibles and inner maxillæ; _e_, labrum; _f_, palpi.

PLATE 24.

_Genera_--CRYPTOPHIALUS AND PROTEOLEPAS.

CRYPTOPHIALUS MINUTUS.