VALVATA. 21 



" this Mollusk deposits its eggs to the number of from 

 sixty to eighty. All are contained in a single spherical, 

 yellowish, leathery capsule, which it fixes to stones and 

 stems of aquatic plants. The eggs are not wholly hatched 

 in the capsule, but about the twelfth day of its existence 

 are partly set free through a rupture of its walls, and 

 till about the sixteenth day, when the fry are set free, 

 are united in a gelatinous mass." 



This shell is generally distributed through the British 

 Isles (though rare in some districts), preferring peaty lo- 

 calities. The variety which has been termed depressa, 

 occurs abundantly in the Curraghs of the Isle of Man 

 (E. F.) ; in the Clumber Lake (Jeffreys) ; and at Dublin 

 (Humphreys). 



It ranges through the greater part of Europe, and is 

 known as a fossil in the later fresh-water tertiaries. 



V. cRisTATA, Miiller. 

 Spire not raised above the last whorl. 



Plate LXXI. fig. 11, 12, 13. 



Valvata cristata, MiJLLER, Hist. Verm. pt. 2, p. 198. — Fleming, Brit. Animals, 

 p. 286. — Alder, Mag. Zool. and Bot. vol. ii. p. 117. — 

 Gray, Manual L. and F. W. Shells, p. 98, pi. 10, f. 115.— 

 Brown, Illust. Conch. G. B. p. 28, pi. 14, f. 66, 67.— 

 ScHROT. Fliissconch. p. 240, pi. 5, f. 26. — Lam. Anim. s. 

 Vert. (ed. Desh.) vol. viii. p. 505. — C. Pfeif. Deutsch. L. 

 und Slissw. Moll. pt. 1, p. 101. — Nils. Moll. Suecice Ter. et 



Fluv. p. 87 Menke, Zeit. Malakoz, 1845, p. 123. 



Nerita valvata, Gmelin, Syst. Nat. p. 3675. 

 Helix cristata, Mont. Test. Brit. vign. 1, f. 7, 8 ; vol. ii. p. 460. 

 Valvata spirorbis, Drap. Moll. Ter. et Fl. France, pi. 1, f. 32, 33. — Turt. 

 Manual L. and F. W. Shells, p. 131, f. 115. — Brard, 

 Coq. Paris, p. 187, pi. 6, f. 15, 16.— C. Pfeif. Deutsch. L. 

 und Susswas. Conch, pt. 1, p. 100, pi. 4, f. 34. 

 „ planorhis, Drap. Moll. Ter. et Fluv. France, p. 41. — Turt. Manual L. 

 and F. W. Shells, p. 132, f. 116. 



