Fig. 



17. C. pisidioides, Gray.—C. cornea, var., Brit. Moll.— Bitches and 



ponds, C. Oblique, and light coloured. 



18. C. rivicola, Leach.— Cardium mix, etc. — Thames, etc. Large, 



oval, wrinkled. 



19. C. caliculata, Drap. — C. lacustris, etc. — Newcastle, Bristol, etc., 



Mr. With a ridge at the apex. 



20. C. lacustris, Drap. — -pallida, Gray. — Regent's Park, etc., Mr. 



Oval, light. 



Pisidium. Inhabits fresh-water. 



21. P. obtusale, Pfeiffer. — P. pusillum, var.? 



22. P. pusillum, Turton, (Tellina.) — Cyclas foniinalis and gibba.— In 



marshes and ponds at various places, C. Includes P. obtustale ? 



23. P. amnicum, Miiller, (Tellina.) — T.rivalis, Cyclas palustris, C. ob- 



liqua. — British rivers, etc., generally. C. obliqua ribbed. 



24. P. nitidum, Jennyns. — Battersea, Swansea, etc., C. Thick, dark, 



blunt. 



25. P. Henslowianum, S/ieppard, (Tellina.) — Cyclas appendiculata, P. 



acutum. — Cambridge, Swansea, etc., R. With a projection on 

 the umbones. 



26. P. pulohellum, Jennyns. — Cyclas foniinalis, etc. — Various locali- 



ties, C. Ridged. 



27. P. cinereum, Alder. —Cyclas c. — Various localities, Mc. Smooth. 



28. P. roseum, Scholtz. — Various loc, with P. pulchellum and P. niti- 



dum, M. C. Subquadrate ; animal pink. 



