54T HAZATLAN BIVALVES 



GENUS ?CLEMENTIA, Gray. 

 B. M. Cat. Yen. p. 197. 



82. ? CLEMENTIA GEACILLIMA, n. s. 



?C. t. subtrigojid, tenuissimd, alba, diaphand, concentrice 

 liratd, liris rotnndis, approximatis ; postice prolongatd. Intus 

 dent. 3-4 diver gentibus, minutis : ligamento vix monstrante. 



This shell comes nearer to dementia than to any other 

 genus I know ; nor is there any reason why it should not be 

 found on the American shores of the Pacific. Some may rank 

 it with Tellina. The teeth are more equally divergent than in 

 the typical species. Long. *09, lat. '13, alt. *5. 



Hob. Mazatlan ; from backs of Chamse and Spondylus La- 

 marckii ; extremely rare ; L'pool Col. 

 Tablet 216 contains 1 perfect and 2 broken valves. 



GENUS TKIGONA, Megerle. 



Trigona, Megerle. teste Desk. S. M. Cat. Ven. p. 4&Muhl- 



feldt, teste Wbodw. Man. Moll. pt. 2, p. 305. 

 =Trigonella, Conr. Hinds. 

 = Cytherea (pars) Lam. 



Known from Cytherea and Dione by the trigonal shape ; 

 numerous irregular cardinal and long lateral teeth ; and by 

 the velvety periostraca outside the epidermis, of a dull white 

 colour, which, being mistaken for dirt, is generally very care- 

 fully cleaned off by collectors. Under the microscope, this 

 appears like an irregular mass of needle-like crystals. 



JL 83. TEIGONA RADIATA, Sow. 



Cytherea radiata, Proc. Zool. Soc. 1835, p. V&.Hanl. Descr. 



Cat. p. 106. Sow. Thes. Conch, p. 619, pi. 128, f. 2831. 



C. B. Ad. Pan. Shells, p. 273, no. 446. 

 Trigona radiata, Desh.-S. M. Cat. Ven. p. 51, no. 19. 

 Yenus Solangensis, B. M. Cat D'Orb. Moll. p. 68, no. 607. 

 Trigona Byronensis, Gray, Anal. t. 8. p. 304, 1838. 

 = Cytherea corbicula, MenJce (non. Lam.) in Zeit.f. Mai. 1847, 



p. 189, p. 54 : also Sow. Thes. Conch, p. 614, no. 7 (pars), 



pi. 128, f. 39 (f. 37, 38 excl.) 



