CREPIDULA. 127 



" In the squama stage it appears as a very thin, flat shell ; with 

 the vertex generall}^ lustrous brown, sometimes white ; from this 

 radiate a greater or less number of brown lines, sometimes more 

 or less brolien into dots, gradually losing themselves in the 

 white texture of the shell, sometimes reappearing at the margin, 

 sometimes altogether absent. Yery rarel}' a rich lustrous brown 

 is developed inside, shading into a sea-weed green. The shell is 

 covered with a copious yellowish green epidermis, which lies in 

 a fringe round the sharp margin. In its ordinary state, the 

 texture has a tendency to run into layers. The epidermis does 

 the same, the layers being in shreds and very copious." 



C. DORSATA, Brod. PI. 37, figs. 26-30 ; PI. 38, fig. 41. 



Thin, wide, irregularly longitudinally corrugated or rudely 

 ribbed, or smoothish, whitish or yellowish, sometimes violaceous 

 within; septum bilobed. Length, -75 inch. 



Mazatlan to California. 



So distorted is this species in some instances that the apex is 

 somewhat distant from the margin, and the attachment of the 

 septum is lateral, so that it was described as a Calyptrjea. 



G. bilobata, Gray (figs. 26, 27), is a smooth, chestnut-rayed 

 form of this species; C lingulata, Gould, is described from a 

 worn specimen of it. G.foliacea (fig. 28), and G. strigata (figs. 

 29, 30), Brod., referred by Carpenter to the next species, appear 

 to me more likel}^ to belong here, if they are not G. aculeata, 

 Gmel. 



C. DiLATATA, Lam. PI. 37, figs. 31-34 ; PI. 38, fig. 42. 



Oval, broad, rather thick, smooth, but with distinct growth- 

 lines ; whitish, under a yellowish brown, thin epidermis, interior 

 white, but the margin usually stained or radiately lineated with 

 chestnut ; apex much curved to the side of the shell. 



Length, l*5-2*5 inches. 



Western Goast of Araerica from Patagonia to Alaska ; 



Kamtschatka. 



Distinguished by its rugose growth, inflated form, interior 

 marginal coloring. The synonj^my is very large : C. depressa, 

 Desh., G. Peruviana^ Lam., G. patula, Desh., G. Adolphsei, 

 Lesson, C. nautiloides^ Lesson, G. pallida, Brod. (fig. 32), G. 

 arcuata (Brod.), Orb., G. princeps, Conr., G. praerupta, Conrad, 



