62 



MOLLUSC A. 



[Gasteropoda 



Genus 13 Emarginula. — Lamarck. 



Shell conical, shield-shaped; destitute of spiral convolutions; 

 vertex inclined to the posterior extremity; anterior margin with 

 a fissure, or notch; internal cavity simple; anterior sides of the 

 muscular impression interrupted, expanded, and not continued 

 across the front. 



1. Emarginula fissura, pi. XII, f. 17 and 19. 



Emarginula Jissura, First Ed., pi. 36, f. 17 and 19; Lamarck, 

 Syst., VI, pt. 2nd, p. 7; Brown, Couch. Text Book, p. 101, pi. 

 14, f. 17; lb., Popular Ency., II, p. 378, pi. 17, f- 97; Patella 

 Jissura, Pennant, No. 152, p. 144, pi. 90, f. 151 ; Donovan, pi. 

 3, f. 2 ; Montagu, p. 490 ; Brown, Wernerian Mem., p. 583 ; 

 Fleming, p. 365; Forbes, p. 33; Martini, I, pi. 12, f. 109, 110; 

 Da Costa, pi. 1, f . 4 ; Maton and Rackett, p. 236; Turton, 

 Brit. Fau., p. 198. 



Shell brownish-white, conic, subpellucid, and rather thick ; 

 surface furnished with longitudinal and concentric striae, pro- 

 ducing a beautiful lainellated appearance ; vertex slightly re- 

 flected; anterior margin provided with a longitudinal fissure, or 

 slit, extending about a fourth of the length of the shell ; inside 

 white, smooth, and glossy, sometimes of a skin colour; aperture 

 oval ; margin slightly crenated. Length half an inch ; height 

 three-eighths, and breadth nearly the same. 



In the young shell the vertex is more reflexed, and in some 

 instances is slightly hooked, turning backwards nearly to the 

 anterior margin. 



The E. Jissura is rather local, and found on the coasts of 

 Dorsetshire, Devonshire, Cornwall, Kent, and Northumberland, 

 in England ; the Frith of Forth and Clyde, Scotland ; and at 

 Portmarnock, Ireland. 



2 Emarginula rosea, pi. XII, f. 21, 22. 



Emarginula rosea, First Ed., pi. 36, f. 21, 22; Bell, Zool. 

 Journ., I, p. 52, pi. 4, f. 1. 



" Shell ovate, cancellated, covered with a fuscous waved epi- 

 dermis; inside rose-coloured; vertex acute, very much incurved 

 and subinvolute, provided with a marginal fissure." — Bell. 



Found in Poole Harbour, by Thomas Bell, Esq., who took 

 three specimens by dredging. 



Genus 1 4 Scissurella. — D'Orbigny. 



Shell subelliptical, subdepressed ; spire short, small, and con- 

 sisting of two or three volutions; aperture suboval, oblique; lip? 

 separated from each other above, on the left side; outer lip 

 sharp on the margin, with an oblong, deep slit, or foramen, 

 situate near the spire, and almost parallel with the suture, and 

 is continued externally as a subcarina ; inner lip somewhat 

 reflected, with a large umbilicus behind it. 



Probably the situation which this genus should occupy, is in 

 the family Turbinacea. 



1. Scissurella crispata. 



Scissurella crispata, Fleming, Brit. An., p. 366. 



"Transversely ribbed, and spirally striated; inner lip reflected 

 on the body volution. 



" Breadth about the fifteenth of an inch; white, and without 

 anv apparent cuticle ; whorls three, increasing rather rapidly 

 from the slightly elevated apex, and sloping with a gentle con- 

 vexity, from the separating line to the keel ; under side with a 



central cavity, from which the whorls extend, a little convex to 

 the keel. The whorls are marked by numerous fine transverse 

 arcuated ribs, narrower than the intervening spaces, crossed by 

 fine longitudinal strise (most conspicuous on the spaces), giving 

 to the shell its pccuHkr reticulated appearance ; the ribs on the 

 upper side are coarser than those below. The aperture is sub- 

 orbicular, slightly depressed ; the outer lip thin ; the inner lip 

 slightly reflected over the cavity, spread on the body whorl, and 

 continuous with the outer lip. From the pillar cavity a shallow 

 gutter extends anteally, and joins the pillar lip ; this is chiefly 

 conspicuous on the largest specimens. The longitudinal slit in 

 the middle of the outer lip extends backwards about two-thirds 

 of the diameter of the shell, where it joins the narrow groove 

 in the keel of the shell which it had formerly occupied. The 

 margin of the slit is slightly elevated, as well as the groove, 

 which is seen winding round the whorls at the separating line, 

 nearly to the apex ; the groove itself is slightly ribbed across. 

 I found this shell in 1809, and specimens then transmitted to 

 Colonel Montagu, were pronounced by him the fry of a Tro- 

 chus, it is, however, a well marked shell, and belongs to the 

 genus Scissurella of M. D'Orbigny." — Fleming. 



Found by the Rev. Dr. Fleming, " in shell sand, at Noss, 

 Zetland, after a storm." 



Family V Semiphyllidiacea. 



Branchiae situate under the margin of the mantle, and set in 

 a longitudinal series, on the right side of the body. The ani- 

 mals respire under water. 



Genus 15 Pleurobranchus Cuvier. 



Shell placed internally on the back of the animal ; halioti- 

 form, thin, flat, and obliquely oval ; convex above, towards the 

 somewhat spiral apex, with a lateral, nearly terminal, depressed 

 vertex ; aperture entire. 



1. Pleurobranchus plumula, pi. II, f. 14, 15. 



Lamellaria plumula, First Ed., pi. 44, f. 14, 15; Pleuro- 

 branchus plumula, Fleming, p. 291 ; Brown, Conch. Text 

 Book, p. 102, pi. 14, f. 14 ; Smith, Wernerian *Mem., VIII, p. 

 43; Bulla plumula, Montagu, p. 214, pi. 14, f. 9; Brown, 

 Ency., VI, p. 435; Turton, Brit. Fau., p. 168; Fleming, Ency., 

 VII, p. 84 ; Maton and Rackett, p. 183. 



Shell oblong-ovate, depressed, very thin and pellucid, of a 

 yellowish horn-colour, with a very small convolution placed 

 near one end ; whole surface strongly wrinkled concentrically, 

 with three radiating indentations, emanating at the apex, and 

 terminating on the lower margin ; aperture the whole length 

 of the shell; inside very glossy, with undulations corresponding 

 to the wrinkles on the outside; pillar slightly inflected, so as to 

 form the depressed volution. Length upwards of half an inch ; 

 breadth more than a quarter. 



Discovered by Montagu on the rocks at Milton Sands, south 

 coast of Devonshire, and has since been found in many parts 

 of England, Scotland, and Ireland. 



2. Pleurobranchus membranaceus, pi. II, f. 9- 

 Lamellaria membranacea, First Ed., pi. 44, f. 9 ; Montagu, 



Linn. Trans., XI, p. 184, pi. 12, f . 3 ; Pleurobranchus mem- 

 branaceus, Fleming, p. 291. 



