114 MAZATLAN BIVALVES 



162. MONTACUTA , sp. ind. 



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

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

 dinal teeth. The lunule is much incurved : indistinct ridges 

 run from the prominent umbo to the anterior and posterior 

 margins ; surface concentrically striated ; hinge margin inter- 

 rupted, with large sunken cartilage pit bounded by 2 marginal 

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

 probably larger than the last. 



Sab. Mazatlan ; off Charna ; L'pool Col. 



FAMILY CYCLADIDJE. 



GENUS CYEENA, Lam. 

 _| . 364. CYEENA OLIVACEA, n. s. 



C. t. corn-press a, subtrigond, Icevi, vel striis incre- 

 menti Jiaud impressis, . epidermide olivaced indutd ; margine 

 ventrali excurvato, posticum versus plerumque sinuato ; postico 

 angulato, subrostrato ; latere dorsali antico declivo, vix alato ; 

 umbonibus satis prominentibus, ligamento elongato ; epidermide 

 umbones tegente, lam e His p arvis corrug atis pler- 

 umque indutd, maxime angul am posticam versus ; intus pur- 

 pured, maxime umbones et rnargirfem versus ; dent. card, iii., 

 quarum alterd valvd antici duo, alterd postici duo, bifidi sunt ; 

 lat. 2-2, 1-1, parvis, Icevibus, extantibus, quarum antici pro- 

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

 angustissimo. 

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



in Cat. Prov. : non D'Orb., ad fid. spec. typ. : nee Phil, in 



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



This shell has been freely distributed as C. Fontainei, 

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

 original types 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. 1844. 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 peaked posteriorly ; 



