612 



aut tribus cardinalibus, uno sublaterali, plerumque approxiino ; 

 epidermide tenui. 



The Cythema are distinguished from the Veneres by the cha- 

 racter of the hinge, there being a short lateral tooth generally 

 close to, but distinct from, the cardinal teeth. In the section of 

 Veneres named Dosina by some authors, there is a rudimentary 

 indication of this character, enough to show the uncertaizity of 

 our artificial classifications, but not enough to invalidate the pre- 

 sent genus as a useful division. After removing the genus Meroe 

 on the one hand, and Circe and Artemis on the other, we can see 

 no practical utility in other generic divisions which have been 

 proposed for the shells now to be described. 



1. CythervEA Crassatelloides (pi. cxxvii. f. 1, 2, 3), 

 Trigona Crassatelloides, Conrad, Ann. Nat. Sc. Phil. vol. vii. 

 p. 253. t. 19. f. 17. Test, junior, Trigona stultorum ? Gray in 

 Analyst, 1838. Hanky, Sp. Shells, p. 105. Wood, Sup. t. 2. f. 2. 



Cyth. testa subtrigona, crassa, subaequilatera, obliqua; cardine 

 et ligainento magnis; margine lateral! postico, obliquo, sub- 

 elongato, margine ventrali prope angulum posticum subarcuato ; 

 colore pallido, radiis fuscis violascentibus, vel griseo-fuscescente ; 

 epidermide pallide fulva, vitrea. 



Shell very thick, with large hinge and ligament ; obliquely 

 shaped, although nearly equilateral ; umbones prominent, ventral 

 outline rather swollen near the posterior angle, which is not very 

 decided or sudden ; colour pale, with rays of brown or purplish ; 

 epidermis pale greenish-yellow, glassy, and smooth ; the teeth and 

 muscular impressions marked with purplish-brown. The younger 

 specimens are probably identical with the C. stultorum, figured in 

 Wood's Index. 



California. Mus. Cuming, Guhba, Sfc. 



2. Cyther/EA dubia (pi. cxxvii. f. 4), Sowerby, jun. 



Cyth. testa C. Crassatelloidi simillima, sed magis angulari et 

 recta ; margine ventrale prope angulum posticum rectiusculo. 



Our figure of this shell is taken from a drawing made long ago ; 

 but we have no idea in what collection the shell is to be found, or 

 from what locality it comes. Mr. Cuming has a shell something 

 like it, but not absolutely identical with it, from China. The 

 species appears much less oblique than C. Crassatelloides, and 

 more angular posteriorly. 



