CONCHACEA.] 



MOLLUSCA. 



95 



I found this new British species immediately under the 

 columnar greenstone rocks, west end of Arthur's Seat, near 

 Edinburgh, plentiful in a ditch at the Wells of Weary, which 

 is now covered up by the railway. 



4. PlSIDIUM APPENDICULATA, pi. XXXIX, f. 25. 



Ct/clas appendiculata, Leach, MSS.; Turton, Man., p. 15, f. 

 6 ; Pisidium Henslowianum, Thompson, Ann. and Mag. Nat. 

 Hist., VI, p. 54; Tellina Henslouinana, Sheppard, Linn. Trans., 

 XIV, p. 150. 



Shell obliquely oval, much inflated; with regular, well defined, 

 concentric grooves ; beaks very tumid, considerably produced, 

 and somewhat tubercled. Length an eighth and a half of an 

 inch ; breadth not quite a quarter. 



Found in slow running streams, but is very rare. 



This shell seems nearly allied to P. obliquum, from which, 

 however, it differs, in its greater convexity, and the protrusion 

 of the beaks, at the base of which is a groove, or dark zone, 

 giving them the appearance of tubercular appendages. 



5. Pisidium nitidum, pi. XXXIX, f. 26. 



Pisidium nitidum, Jenyns, Monog., p. 16, pi. 20, f. 7, 8; 

 Thompson, Ann. and Mag. Nat. Hist., VI, p. 53. 



Shell suborbicular, or slightly oval; umbones large, and blunt; 

 external surface very glossy, of a pale horn-colour, and covered 

 with fine, concentric striae, which are wider-set and deeper on 

 the umbones. 



Inhabits Battersea Fields, some ditches in Cambridgeshire, 

 and ditches near Worcester; in a pond at Wolf hill, near Belfast, 

 and other places in that neighbourhood ; Lough Gill, County 

 Sligo, Portarlington, and Finnoe, Ireland. 



6. Pisidium pusillum, pi. XXXIX, f. 27- 



Pisidium pusillum, Jenyns, Monag., p. 14, pi. 20, f . 4 and 6; 

 Thompson, Ann. and Mag. Nat. Hist., VI, p. 53 ; *Cyctas pu- 

 silla, Turton, Brit. Biv., p. 251, pi. 11, f. 16, 17 ; lb., Man., p. 

 16, pi. 1, f. 7; Alder, Mag. Zool. and Bot., II, p. 119. 



Shell nearly orbicular, slightly ovate, subcompressed ; um- 

 bones prominent, and very obtuse at the points; sides some- 

 what flattened, and very slightly inequilateral ; surface of an 

 olivaceous-brown, with very fine, concentric striso. 



Inhabits ponds near London, and many other localities. In 

 Ireland, according to Thompson, it is the most common of the 

 genus, frequenting ponds and drains. 



7. Pisidium cinereum, pi. XXXIX, f. 28. 



Pisidium cinereum, Alder, Cat. Sup., p. 4 ; lb., Mag. Zool. 

 and Bot., II, p. 119; Thompson, Ann. and Mag. Nat. Hist., 

 VI, p. 54. 



Shell compressed, subovate ; umbones but slightly produced, 

 obtuse at the points, is sometimes capped ; lower margins of 

 the valves meeting at an acute angle ; surface of a grayish ash- 

 colour, and finely striated concentrically; with a few super sulci, 

 which form deeper transverse zones. 



This shell is more ovate in its form than any of its conge- 

 ners, excepting the P. obliquum, and will be at once recognized 

 by being more compressed than them, and by its ashy hue. 



Variety 1. Somewhat more ventricose, with the umbones a 

 little more produced. 



Inhabits ponds near Newcastle, and other localities in the 

 North of England. Mr. Thompson says it is widely spread 

 throughout Ireland, although no where common. He par- 



ticularizes Holywood House, Downshire; Youngrove, near 

 Middleton, County of Cork, by Miss M. Ball; Killereran, 

 County of Galway, and Portarlington, by the Rev. B. J. 

 Clarke; and neighbourhood of Dublin, by Thomas William 

 Warren, Esq. 



Sub-Division — Tenuipedes. 



The mantle barely united before ; foot small, narrow, and 

 compressed ; shell having but a moderate gape. 



Family I Nymph acea. 



Having never more than two primary teeth in the same 

 valve; shell often gaping slightly at the lateral extremities; 

 ligament external ; umbones generally projecting outwards. 



Section I. — Destitute of lateral teeth. 



Genus 17 Crassina. — Leach. 



Shell suborbicular, transverse, equivalve, inequilateral; hinge 

 with two strong, divergent, primary, large, central teeth in the 

 right valve, and one small, nearly obsolete tooth, together with 

 an indistinct, lateral one in the left valve; two ovate or oblong, 

 remote, lateral, simple, muscular impressions in each valve, with 

 a third very small one, situate immediately below the indistinct 

 lateral tooth, or at the end of the posterior external depression, 

 and in some instances mingling with the lower termination of 

 the posterior muscular impression, which is always simple, and 

 not sinuated. 



1. Crassina Danmoniensis, pi. XXXVIII, f. 1. 



Crassina Danmoniensis, First Ed., pi. 18, f. 1 ; Lamarck, V, 

 p. 554 ; Venus Danmonia, Montagu, Sup., p. 45, pi. 29, f. 4 ; 

 Crassina sulcata, Turton, Biv., p. 131, pi. 11, f. 1, 2; Astarte 

 Danmonia, Fleming, p. 440 ; Astarte Danmoniensis, Forbes, 

 p. 50. 



Shell strong, thick, subcordiform, subcompressed; with many 

 regular, obsoletely striated, strong, equidistant, transverse ribs ; 

 intervening furrows rather deep, quite smooth; umbones nearly 

 central, anteriorly reclined, and rather acute, with a deep, 

 lanceolate lunule under them ; surface covered with a dark 

 reddish-brown, strong epidermis ; inside white, but not glossy, 

 except round the margin, which is finely crenated, and very 

 blunt at the edge. 



Found on the Devonshire, Welsh, and Northumberland 

 coasts; also the Friths of Forth and Clyde; Lough Strangford 

 and Portmarnock, Ireland. 



2. Crassina Scotica, pi. XXXVIII, f. 9. 



Crassina Scotica, First Ed., pi. 18, f. 9; Turton, Biv., p. 130, 

 pi. 1 1 , f. 3, 4 ; Venus Scotica, Montagu, Sup., p. 44 ; Maton 

 and Rackett, p. 81, pi. 2, f . 3 ; Lamarck, V, p. 600; Astarte 

 Scotica, Fleming, p. 440; Forbes, p. 51. 



Shell thick, subcordiform, subcompressed ; umbones nearly 

 central, considerably reclined anteriorly; beneath them a lance- 

 olate, subcordiform lunule ; surface with many regular, rather 

 elevated, somewhat parallel, transverse ribs, which are narrowed 

 towards the posterior side ; whole surface covered with a thick, 

 yellowish-brown epidermis, but reddish-brown in others; inside 

 smooth, white ; with the margin plain. 



