132 



MOLLUSCA. 



waved ; surface with regular, well defined, divergent, longi- 

 tudinal, moniliform stria;, 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. 



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. 



I. 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 (Pcge 63.) 



3. Patella fulva, Miiller, Zool. Dan., I, pi. 24, f. 1, 2, 3. 



Patella Forbcsii, page 64. 



CLASS CONCHIFERA. 



Genus Pecten. — (Page 71.) 



16. Pecten Isabella. 



Pecten Isabella;, Macgillivray, Moll. Ab., p. 225. 



Shell ovate, rounded, nearly equivalve, slightly convex ; 

 having twenty-four slender, compressed, rounded ribs, with 

 very numerous, thin-edged lamella;, which towards the margin 

 are elevated into triangular, compressed, acute spines ; the 

 interstices with transverse, scalar lamella?; 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 Ascidiae and coral- 

 lines, from the Aberdeenshire coast. 



Genus Modiola (Page 77.) 



7. Modiola Ballii, pi. XXXVII, f. 36. 



Shell transversely oblong-ovate ; umboncs 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 stria;, the intervening furrows broader, 

 smooth, and glabrous, with several well marked lines of 

 growth; hinge line a little arcuated; colour grejish-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 

 pidchellum, var., Jenyns. 



Shell transversely and obliquely ovate, somewhat tumid, very 

 thin, and glossy ; with regular, distinct, concentric stria?, a few 

 more conspicuous lines of growth, and very faint radiating 

 striulsB ; umbones tumid, obtuse, considerably nearer the ante- 

 rior side, which forms about a third of the segment of a circle, 



