BIVALVE SHELLS. 21.') 



Cycladea, Desk. (1830) Enc. Mefh. ii.; Tab. de Class, des Moll. 



Meiike (1830), Si/n. Meth. Moll. p. 110. 

 Cycladia, Rafin. (1820) Coq. Biv. de VOhio. 

 Cycladae, Flem. (1828) Brit. Anim. p. 409. 



Gray (1840), Turt. Man. ed. 2. p. 277. 

 Cycladina, Latr. (1825) Fam. Nat. p. 218. 



Macgill. (1844) Moll. Aberd. p. 208. 

 Cyclasida;, D'Orb. (1846) Foy. en Amer. Moll. p. 566. 

 Cycladacea, Hinds (1844), Zool. Sulph. p. 66. 

 VeneriadEe (ex parte), Leach (1818), Ann. SfMag. Nat. Hist. xx. 



272; (1852), ed. Gray, Syn. Moll. Brit. p. 286. 

 Cyrenida;, Gray (1840), Syn. Brit. Mus. p. 76, 91. 

 Corbiculadffi, Gray (1847), Proc. Zool. Soc. p. 184 ; (1851) List 

 of Brit. Anim. p. 16; Ann. Sf Mag. Nat. Hist, ser.2. xi. 38. 



" CorbiculadeB. Cardinal teeth 3 • 3 or 2 • 2, diverging ; lateral 

 teeth compressed. Sijihonal inflection none. Periostraca oHve, 

 hard, brittle, often polished. Siphons contractile. 



A. Cardinal teeth 3 • 3, front of right and hinder of left valve 

 smallest. Shell solid. 



1. CoRBicuLA, Megerle, Gray, P. Z. S. 1847, n. 552. Shell 

 subcordate ; lateral teeth compressed, subequal, finely 

 striated. C. fluminea. 



2: Batissa. Shell subcordate ; lateral teeth compressed, stri- 

 ated, front very short, hinder elongate. B. tenebrosa. B. 

 obesa, Hinds. 



3. Velorita, Gray, Syn. B. M. 1842, p. 75; P. Z. S. 1847. 



n. 554. Shell cordate, triangular, thick ; teeth large, late- 

 ral, very finely striated, anterior very large, angular, hinder 

 elongate, compressed. V. Cyprinoides. 



4. Cyrena, Lamk. Gray, P. Z. S. 1847, n. 553. Shell sub- 



cordate ; lateral teeth smooth, front roundish, hinder rather 

 comj)ressed. C. Zeylanica. 



B. Cardinal teeth 2 ■ 2, moderately diverging , front of right valve 

 and hinder of left valve smaller j lateral teeth elongate, com- 

 pressed, smooth ; of right valve double, of left valve simple. 

 Shell thin. 



5. SpH^RiuM, Scopoli, Gray, P. Z. S. 1847, n. 555. Shell 

 oblong, cordate, equilateral ; siphon of animal separate, di- 

 verging at the tip. S. corneum. 



10* 



