In the dentition of the right v,nlve this grnus resembles Cochdon^ 

 except that the posterior lamina is greatly developed, resembling a 

 clavicle. The left valve wants the central tooth and chamber of tliat 

 genus. This structural deficiency, however, is compensated by the 

 development of an ossicle in the long cartilage. As far as is known, 

 all the species are from North and Central Amedca, and are swollen 

 ventrally. 



2. Clidiophora cristata. 



C. t. securiformi, minus transversa, tenni, suhplanata ; umboni- 

 bus ad ^ longitudinis sitis ; ventral iter viuxime excurvata ; 

 marginibus dorsalUms, post, maxime incurvato, ant. hie et illic 

 alulis triangularibus cristato : intus marginibus posficis utra- 

 que in valva ereetis : v. dextr. dente postico satis tongo, cica- 

 trice addiictoris tenus haud porrecto ; dente centrali extante ; 

 dente antico a margine separata, usque ad cic. anticam porrecto, 

 haud extante : v. sinistr. dente post, bijido, haud extante, al- 

 terum recipiente, fossa cartilaginea contigua ; d. centr. nulla; 

 d. ant. satis extante, usque ad cicatr. anticam porrecto ; linea 

 palliari a margine valde remota, regulariter in puncta divisa ; 

 radiis ab umbonibus usque ad puncta conspicuis, cequalibus ; 

 ossiculo tenui, elongato. 

 Long. 1-0, lat. •(), alt. -1 poll. 



Hab. in sinu Californiensi ; legit Conway Shipley diligentissimus; 

 sp. un. in Museo Cumingiano. 



This species is known from C. clavicnlata by the much greater 

 posterior curvature of the beaks, and anteriorly by the beautiful tri- 

 angular wing-like serrations of the margin, in which it resembles 

 Tellidora burneti. The inside has elegant rays from the umbo to 

 the dotted pallial line. 



3. Clidiophora tabacea, Meusch. (Mus. Gron.). 



Specimens under this specific name are preserved in the Cumingian 

 collection. 



3 a. Clidiophora trilineata, Say {Pandora tr.), Hani. Rec. 

 Shells, p. 49. 



3 b. Clidiophora nasuta. Shy. (Pandora n.), Sp. Conch, f, 

 18, 19. 



It is probable that these are simply varietal forms of the well-known 

 New England species. Say's name and Sowerby's excellent figure 

 prove that the peculiar hinge of the genus was observed by both 

 authors. Mr. Cuming gives "Philippines" as the habitat of his 

 specimens of C. nasuta, probably in error. Mr. Hanley quotes it as a 

 synonym of C. trilineata. An examination of a large series from Staten 

 Island proves that the outline varies considerably. The tablet in 

 the Nuttallian collection at the British Museum, marked Pandora 

 punctata, belongs to this species. Young shells, when quite perfect, 



226 





