132 
MOLLUSCA. 
waved; surface with regular, well defined, divergent, longi- 
tudinal, moniliform strise, or presenting the appearance of two 
undulating lines intersecting each other, and faint lines of 
growth. Length a quarter of an inch; breadth an eighth. 
Common in deep water, off Aberdeen. 
I 
Genus 7- — Halia. — Risso. 
Shell subovate, spire short, convex, obtuse, volutions rapidly 
diminishing, separated by an impressed suture; body very 
large, tumid ; aperture large, subovately-trigonal, acute above, 
curved below, and terminating in a rather wide notch ; outer 
lip thin ; inner lip formed by the thin-edged, sinous columella 
before, destitute of an umbilicus. 
This genus to follow Utriculus, page 58. 
1. Halia Flemingiana. 
Halia Flemingiana, Macgillivray, Moll. Ab., p. 189. 
Shell thin, brittle, glossy, semitransparent, subovate; spire 
consisting of three convex volutions, separated by a distinct 
suture, and terminating in a very obtuse apex ; aperture sub- 
ovately-trigonal, two-thirds of the entire length, contracted 
above ; outer lip with a thin margin, and forming the fourth of 
a circle ; inner lip sinous, its superior half formed by the body- 
volution, the inferior by the thin flexous edge of the columella, 
the lower extremity curved to the left in a short and rather 
wide canal; colour pure white. Length upwards of half an 
inch ; diameter half its length. 
Found by Mr. James Smith, in deep water, off Aberdeen. 
Genus Patella. — (P*ge 63.) 
3. Patella fulva, Muller, Zool. Dan., I, pi. 24, f. 1, 2, 3. 
Patella Forhesii, page 64. 
CLASS CONCHIFERA. 
Genus Pecten. — (Page 71.) 
16. Pecten Isabella. 
Pecten Isahellce, Macgillivray, Moll. Ab., p. 225. 
Shell ovate, rounded, nearly equivalve, slightly convex ; 
having twenty-four slender, compressed, rounded ribs, with 
very numerous, thin-edged lamellae, which towards the margin 
are elevated into triangular, compressed, acute spines; the 
interstices with transverse, scalar lamellae; ears very unequal, 
being in length as one to two, with divergent sulci, transversely 
lamellate, and echinated ; margins of the upper valves under 
the auricular process provided with four conical spines, and 
a series is continued on the surface to the umbo, which is 
smooth and glossy ; colour white, lower valve tinged with pink. 
Length three-twelfths of an inch ; breadth somewhat less. 
“ This most beautiful Pecten cannot be at all confounded 
with Pecten varius or Pecten niveus, to which it is allied in its 
mode of echination.” 
Found by Professor Macgillivray, among Ascidise and coral- 
lines, from the Aberdeenshire coast. 
Genus Modiola. — (Page 77.) 
7. Modiola Ballii, pi. XXXVII, f. 36. 
Shell transversely oblong-ovate; umbones placed very near 
to one side ; a slight groove or furrow emanates from the um- 
bones, and terminates in an oblique line on the margin of the 
anterior side, on which the colour is golden-yellow ; covered 
with a very glossy, olivaceous' epidermis, which in certain lights 
exhibits a metallic lustre ; inside highly pearlaceous, with trans- 
verse wrinkles towards the extremity ; the surface exhibiting 
gold and coppery metallic reflections, and studded with a num- 
ber of small circular pits, like those left by the small-pox. 
Found at Yougal, by Robert Ball, Esq. 
Genus Cyclas. — (Page 93.) 
5. Cyclas citrina, pi. XXXVII, f. 37. 
Cyclas Jlavescens ? Macgillivray, Moll. Ab., p. 246. 
Shell very thin, subdiaphanous, and slightly elliptical ; very 
ventricose, a little inequilateral, nearly hemispherical; umbones 
large, prominent, inflated, and rounded ; covered with a rather 
dull citron-coloured epidermis, beneath which the surface is 
irregularly and strongly striated concentrically, with two or 
three lines of growth. 
Discovered by Thomas Glover, Esq., of Smedley Hill, Man- 
chester, in the Leven, a little way below the Lake of Winder- 
mere, Westmorland. Length about two and a half eighths of 
an inch. 
This shell differs from Cyclas cornea, in being more orbicu- 
lar, in the umbones being much larger, more prominent, and 
bulging, and it never attains so large a size as that species. 
Genus Pisidium. — (Page 94.) 
7. Pisidium Joannis. 
Pisidium Joannis, Macgillivray, Moll. Ab., p. 248. 
Shell transversely-ovate, moderately convex, thin, glossy; 
both sides well rounded ; umbones tumid, obtuse, with smooth 
beaks, and placed nearest the anterior side ; whole surface with 
numerous, concentric strije, the intervening furrows broader, 
smooth, and glabrous, with several well marked lines of 
growth ; hinge line a little arcuated ; colour greyish-yellow. 
Length two-twelfths of an inch ; breadth two and a half 
twelfths. 
Found by Mr. Leslie, in a ditch and pond of the Professor 
of Medicine, and afterwards by Professor Macgillivray, in a ditch 
near the Links of Old Aberdeen, where it is very abundant. 
8. Pisidium Jenynsii. 
Pisidium Jenynsii, Macgillivray, Moll. Ab., p. 249; Pisidium 
pulchellum, var., Jenyns. 
Shell transversely and obliquely ovate, somewhat tumid, very 
thin, and glossy ; with regular, distinct, concentric strias, a few 
more conspicuous lines of growth, and very faint radiating 
striula 3 ; umbones tumid, obtuse, considerably nearer the ante- 
rior side, which forms about a third of the segment of a circle, 
