126 CREPTDUtA. 



This species differs in form from the last as C. glauca does 

 from C. convexa. 



C. PORCELLANA, Linn. PI. 37, fig. 22. 



Apex slightly beaked, whitish, maculated and divaricately 

 stained with purplish chestnut spots. Length, 1-25 inches. 



Senegal ; Indian Ocean ? 



It is very doubtful whether this is distinct from G. fornicata ; 

 a sharper apex and divaricating color-lines appear to be its chief 

 points of difference. 



C. MOULINSI, Michaud. PL 36, fig. 17. 



Oval, depressed, smooth or slightly rugose, chestnut-brown. 



Length, 1-1-25 inches. 



Mediterranean Sea. 



Is C. fornicata, Phil, and C. gibbosa, Desh. Dr. Jeffreys and 

 other good authorities consider this to = C. fornicata. 



C. LESSONIT, Brod. PI. 36, figs. 18-21 ; PI. 37, figs. 22-25. 



Rather flat, concentrically laminarly frilled, frequently ra- 

 diately costulate, white, sometimes radiately lineated with chest- 

 nut. Length, 1 inch. 



West Coast of Central America to Monterey, Cat. 



C. fimbriata, Reeve (figs. 20, 21), said to come from "Van- 

 couver's Straits," C. squama, Brod. (fig. 23), C. nivea, C. B. Ad., 

 C. striolata, Menke, and probably C. navicelloides and C. 

 exuviata, Nutt., C. explanata, Gould (figs. 24, 25), and C. per- 

 forans, Yal., are synqnyms. C. explanata has the form of C. 

 unguiformis, but Carpenter places it here. 



Carpenter (Mazat. Cat., 281), describing this species under 

 Prof. C. B. Adams' name of G. nivea, writes as follows con- 

 cerning it : 



' This creature, when flat 'and finely grown, is the C. squama 

 of Broderip. The same shell, when coarsely grown, more convex 

 and without brown stripes, is C. nivea, C. B. Ad. When the 

 layers of which it is composed, instead of lying regularly one 

 over the other, are slightly prominent, it becomes C. striolata, 

 Mi-iike. When they are drawn forwards and project it becomes 

 C. Lessonii, Brod. The name of Prof. Adams is retained, in 

 preference to the prior ones of Broderip and Menke, as repre- 

 senting the normal condition of the shell. 



