nsiDiUM. 131 



come from the gently flowing Main, near its junction with 

 Lough Neagh (Thompson) ; it is found at Killarney 

 (Barlee), Cork (S. Wright, jun.), &c. &c. Capt. Brown, 

 who first distinguished it as a British species, states that his 

 specimens came from a ditch at Duddingston Loch, near 

 Edinburgh, and from another at Hunter's Bog, King's Park. 

 Professor Macgillivray enumerates it among his Aberdeen- 

 shire Mollusca. Its foreign distribution is uncertain. 



P. henslowianum, Sheppard. 



The urnbones furnished with a lamelliform projection. 

 Plate XXXVII. fig. 11. 



Tellina He/isloiviana, Sheppard, Linn. Trans, vol. xiv. p. 150. 

 Cyclas appendiculata, Turt. Manual L. and F. W. Shells, vol. xv. pi. 1, f. <>. 

 — Hanley, Recent Shells, vol. i. p. 91, suppl. pi. 14, 

 f. 42 (copied from last). 

 Pisidium Henslowianum, Jenyns, Trans. Cambridge Phil. Soc. vol. iv. p. 308, 

 pi. 21, f. 6, 7, 8, 9.— Gray, Manual L. and F. W. 

 Shells, p. 285, pi. 1, f. G.— Brown, 111. Conch. G. 

 B. p. 95, pi. 39, f. 25. 

 Pisidium naif um, L. Pfeiffer, Wiegm. Archiv. f. Naturg. 1831, pt. 1, p. 230. 



There is very little to distinguish this species from 

 pidchellum (to which eventually it may possibly be 

 united) except the very extraordinary appendage upon 

 the urnbones. The shape is obliquely ovate, and very in- 

 equilateral ; the valves are not very ventricose (in some 

 exotic ones they are rather compressed), and are of a horn or 

 yellowish horn colour, and more or less closely striolate in 

 a concentric direction. The surface seems generally more 

 or less glossy ; the ventral margin is moderately curved and 

 rises the more behind. The produced anterior side tapers 

 both above and below to a rounded tip, which lies usually 

 rather below the middle ; its upper edge is rather the less 



