a^k 



FAMILY CAKDIACEA. 233 



6. Pisidium pulchellum. Pretty Pisidium. 



Shell ; obliquely orbicular, ventricose, sometimes rather com- 

 pressed, dull horny, concentrically more or less 

 prominently striated, very inequilateral, anterior O 



side obliquely produced, posterior abruptly trun- 

 cate ; umboes sometimes obtuse, sometimes rather 

 acute. 

 Cyclas fontinalis, Brown (1827), Edin. Journ. Nat. Sci. part 



i. p. 125. pi. i. f. 6, 7 (not of Draparnaud). 

 Pisidium pulchellum, Jenyns (1833), Trans. Phil. Soc. Cainb. 



vol. iv. p. 306. pi. xxi. f. 1 to 5. 

 Cyclas pulc/iella, Hanley (1843), Pec. Piv. Shells, vol. i. p. 91. 

 Pisidium Joannis and Jenynsii, Macgillivray (1843), Hist. Moll. Aberd. 



p. 248, 249. 

 Pisidium fontinale, Brown (1845), Illus. Conch, p. 94. pi. xxxix. f. 23. 

 Pisidium calyculatum, Gassiesianum, Iratianum, and Normandianum, 



Dupuy (1849), Cat. Extram. Test. p. 229 to 235. 

 Pisidium limosum, G-assies (1849), Moll, de VAgen. p. 206. pi. ii. f. 10, 11. 

 Pisidium tetragonum, Normand (1854), Coup d'oeil Cycl. p. 5. 

 Pisidium Casertanum var., Moquin-Tandon (1855), Hist. Moll. vol. ii. p. 



584. pi. lii. f. 24 to 32. 

 Pisidium fontinale var., Jeffreys (1862), Brit. Conch, p. 20 (not of Dra- 

 parnaud) . 

 Hah. Central and Southern Europe. Throughout Britain. (In ditches, 

 drains, and other stagnant water, frequently among the roots of aquatic 

 plants.) 

 P. pulchellum, the smallest of our Pisidia, is regarded by some 

 naturalists as a variety of P. Casertanum, but there are few who 

 participate in that opinion. Though it differs Httle except in being 

 smaller, and of a less triangular form, the species is easily recog- 

 nized. Mr. Macgillivray divides it into as many as three species. 

 His observations on the habits of the animal are among the best 

 that have been made. Speaking of specimens observed in abund- 

 ance in a ditch, in the neighbourhood of Aberdeen, he says, 

 " When advancing in the water, the animal opens its valves a little, 

 places itself erect by means of the foot, which it gradually protrudes 

 until it considerably exceeds the shell in length. It then contracts 

 and drags the shell quickly forward, after which it is again extended 

 and again contracts. It is not always stretched out in a direct line, 

 but is moved in an undulating manner, often from side to side, and 

 appears to act as a tentacle as well as an organ of motion. The 



