114 MAZATLAN BIVALVES 



162. MoNTACUTA , sp. ind. 



Tablet 504 contains a fragment of a stout shell, in many 

 respects like ? !M. subqnadrata ; but entirely destitute of car- 

 dinal teeth. The lunule is much incurved : indistinct ridges 

 riui from the xirominent ximbo to the anterior and posterior 

 margins ; surface concentrically striated ; hinge margin inter- 

 rupted, with large sunken cartilage pit bounded by 2 marginal 

 callosities, biit no lateral teeth. The shell when perfect was 

 probably larger than the last. 



JEah. — Mazatlan ; off Chama ; L'pool Col. 



Fa^iily CYCLADID^. 



Genus CYHENA, Lam. 

 364. Cteena olivacea, n. s. 



C i. compress a, suht rig on a, IcBvi, vel striis incre- 

 menti Jiaud impressis, epiderm'ule olivaced indutd ; margine 

 ventrali excurvato, postieiim versus plerum que sinuato ; postico 

 angulato, suhrostrato ; latere dorsali antieo deelivo, vix alato ; 

 umhonilms satis prominentihus, ligamento elongato ; epidermide 

 umhones tegente, lam ell is par vis corrug atis pler- 

 umque indutd, maxime angulam posticam versus ; intus pur- 

 purea, maxime umhones ef marginem t^ersus ; dent. card, iii., 

 quaf'um altera valvd antici duo, alterd postici duo, hifidi sunt ; 

 lat. 2-2, 1-1, jjarvis, Icviribus, extantibus, quarum antici pro- 

 pinqui, postici remoti sunt; sinu palUi parvo, triangulari, 

 angu^tissimo. 

 = C. Fontaine!, Desk. ms. in B. M. et Mus Cuming, et P. P. C. 



in Cat. Prov. : non 1/Orh., ad fid. spec. t3-p. : nee Phil, in 



Zeit.f. Mai. 1851, p. 70, no. 93. 



This shell has been freely distributed as C. Fontainei, 

 B'Orb., on the authority of M. Deshayes, who having the 

 original ty\yes to consult, was supposed to be correct. The 

 true C. Fontainei, however, is a more regularly formed shell, 

 with faint concentric ribs and a glossy epidermis, and appears 

 identical with C. placens, Hani. 1841. The species which Philip- 

 pi has described under the same name is distinct from either : 

 it may prove to be the following. C. olivacea is known out- 

 wardly by its flattened form, generally beaked posteriorlj- ; 



