FAMILY CARDIACEA. 



229 



Pisidium Grateloupianum, Norinand (1854), Coup d'ceil Cycl. p. 4. 

 Musculium amnicum,-Ada,ms (1858), Gen. Pec. Moll. vol. ii. p. 451. 

 Sab. Throughout Eiu'ope. Siberia. North Africa. (In gentle streams 

 and lakes.) 



This Pisidium is much larger than any other species, and may be 

 recognized, not only by its size, but by its compressed oblique form 

 and concentric sculpture. Its proportions are more than usually 

 inequilateral, the anterior side being produced into an elongately 

 sloping angle, rounded, while the posterior is shortly truncated. 

 The animal is dingy white ; the foot, it may be observed in our 

 vignette, is large ' and extensible, broad at the base, somewhat 

 pointed at the extremity. 



Pisidium amnicum is found in all parts of the British Isles, on 

 the muddy bottom of streams ; it does not seem fond of crawling, 

 but moves its capacious foot about in all directions, and often buries 

 itself. It appears throughout the Continent, passing into Siberia 

 and North Africa. 



2. Pisidium obtusale. Obtuse Pisidium. 



Shell ; suborbicularly ovate, thin, ventricose, dark yellowish green, 

 moderately concentrically striated, nearly equila- 

 teral, both sides rounded, the anterior a little ob- 

 liquely enlarged, umboes obtusely tumidly round- 

 ed and rather prominent. 



Tellina minuta, Studer (1789), Coxe, Trav. in Sivitz. vol. iii. 

 p. 439 (without characters). 



Oyclas obtusalis, Lamarck (1818), Anim. sans vert. vol. v. 

 p. 559. 



Cgclas minima, Studer (1820), Ktirz. Verz. p. 93. 



Pisidium obtusale, C. Pfeiffer (1821), Deutsch. Moll. vol. i. 

 p. 125. pi. v. f. 21, 22. 



Oyclas gibba, Alder (1830), Trans. Nat. hist. Soc. NortJiumb. vol, i. p. 41. 



Pisidium fontinale var., Held (1837), Isis, p. 306. 



Cyclas fontinalis var., Dupuy (1843), Moll, du Gers, p. 89. 



Pisidium ventricosum, Prime (1852), Pro. Nat. Hist. Soc. Boston, U.S. 

 p. 10. pi. xi. 



Pisidium pusillum var., Jeffreys (1859), Ann. Nat. Mist. vol. iii. p. 37. 



Hob. Throughout Europe, principally the central parts. United States. 

 (In shallow pools, drains, and swamps.) 



