62 
MOLLUSCA. 
[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, Conch. Text Book, p. 101, pi. 
14, f. 17; Ib., 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 lamellated 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 14 — Scissurella D’Orbigny. 
Shell subelliptical, subdepressed ; spire short, small, and con- 
sisting of two or three volutions; aperture suboval, oblique; lips 
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 
any 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 striai (most conspicuous on the spaces), giving 
to the shell its peculiar 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 — Pleuro'branchus 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. 1 83. 
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. 
