1864.] DR. P. P. CARPENTER ON THE PANDORIDA, 597 
In the dentition of the right valve this genus resembles Calodon, 
except that the posterior lamina is greatly developed, resembling a 
clavicle. The left valve wants the central tooth and chamber of that 
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 America, and are swollen 
ventrally. 
2. CLIDIOPHORA CRISTATA. 
C. t. securiformi, minus transversa, tenui, subplanata ; umboni- 
bus ad 2 longitudinis sitis; ventraliter maxime excurvata ; 
marginibus dorsalibus, post. maxime incurvato, ant. hic et illic 
alulis triangularibus cristato : intus marginibus posticis utra- 
que in valva erectis: v. dextr. dente postico satis longo, cica- 
trice adductoris tenus haud porrecto; dente centrali extante ; 
dente antico a margine separato, usque ad cic. anticam porrecto, 
haud extante: v. sinistr. dente post. bifido, haud extante, al- 
terum recipiente, fossa cartilaginea contigua ; d. centr. nullo ; 
d. ant. satis extante, usque ad cicatr. anticam porrecto ; linea 
pallidri a margine valde remota, regulariter in puncta divisa ; 
radiis ab umbonibus usque ad puncta conspicuis, equalibus ; 
ossiculo tenui, elongato. 
Long. 1°0, lat. °6, alt. -1 poll. 
Hab. in sinu Californiensi ; legit Conway Shipley diligentissimus; 
sp. un. in Museo Cumingiano. 
This species is known from C. claviculata 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. CiipiopHoRA TABACEA, Meusch. (Mus. Gron.). 
Specimens under this specific name are preserved in the Cumingian 
collection. 
3a. CLIDIOPHORA TRILINEATA, Say (Pandora tr.), Hanl. Rec. 
Shells, p. 49. 
36. CuipiopHora NasutTa, Sby. (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 asa 
synonym of C. ¢rilineata, 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, 
