122 CONCHACEA. 



Sliell compressed, subovate ; umbones but slightly produced, 

 obtuse at the points, where it is sometimes capped ; lower mar- 

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

 ash-colour, and finely striated concentrically; with a few deeper 

 sulci, which form deeper transverse zones. 



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

 geners, excepting the Pisidium ohliquum, and will be at once 

 recognized by being more compressed than any of them, and 

 by its ashy hue. 



Variety/ 1. Somewhat more ventricose, with the umbones a 

 little more pi'oduced. 



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; Klllereran, 

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

 Clarke ; and neighbourhood of Dublin, by Thomas William 

 Warren, Esq. 



8. Pisidium Joannis. 



Pisidium Joannis, Macgillivray, Moll. Ab., p. 248 ; Brown, 

 lUust. Conch., p. 132. 



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 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. 



9. Pisidium Jenynsii. 



Pisidium Jenynsii^ Macgillivray, Moll. Ab., p. 249; Pisidium 

 pulchellum, var., Jenyns ; Brown, Illust. Conch., p. 132. 



Shell transversely and obliquely ovate, somewhat tumid, very 

 thin, and glossy ; with regular, distinct, concentric striaj, a few 

 more conspicuous lines of growth, and very faint radiating 



