GUNDLACHIA. 



149 



Guiidlacliia califoruica, Rdwell. — Shell with the aperture 

 suboval, obliquely expanded towards the left, posteriorly rounded, and 

 wider anteriorly. Internal shelf reaching forward about one-fifth the 

 length of the shell, its margin slightly concave and oblique. 

 Dorsal surface convex, becoming somewhat keel-shaped to- ^^S- ^''^^ 

 wards the apex, which is strongly and obliquely deflected so I 



as to make the right border nearly a straight line, while the "^ 



expansion on the left projects nearly as far back as the apex 

 at an obtuse angle. Structure corneous, with strong concentric 

 lines of growth and faint radiating strije. Color dark brown, 

 opaque ; inner surface shining and purplish, the plate white 

 towards the edge, and in some specimens showing a thickened, 

 white semicircle continuous with its margin across the arch 

 of the shell. Length about sixteen one hundredths, breadth 

 eight one hundredths, and height six one hundredths of an 

 English inch. 



More than fifty specimens were found on water plants in 

 clear stagnant ponds, two or more often stickiig on the back 

 of a larger one. 



The discovery of this little shell in California is of great 



interest, the only species hitherto known being found in Cuba. f''"'»'*'"c/Ma 

 _, . californica. 



1 he generic characters of this shell are strictly paralleUwith 



that species, while those mentioned as specific easily distinguish it. The 

 Cuban shell is more elongated, regularly oval, the apex projecting con- 

 siderably beyond the margin of the aperture, which is not obliquely ex- 

 panded posteriorly. Its size is about one-fifth larger than that of ours. 

 According to Bourguignat, the young shell is a simple obtuse cone, with a 

 semicircujar aperture formed by the edge of the shelf, and the thickened 

 dorsal margin ; but as it grows the animal changes the form of the aper- 

 ture until the opening beneath the shelf becomes like the small end of a 

 broad funnel, which in some of our specimens is still shown by the white 

 semicircular ring. 



The shell much resembles that of the marine Crypta (^Crepidula}, and 

 also Navicella of tropical estuaries ; but the animal is quite 'different in 

 the Cuban species, and will undoubtedly prove so in the Californian. 

 {RoweU.) 



Gundlachia californica, Rowell, Proc. Cal. Acad. Nat. Se. Ill, 21, March, 

 1863. 



I have seen no specimen of 

 this shell whose original de- 

 scription and figure are copied 

 above. Fig. 251 is drawn 

 from an authentic specimen 

 received by Dr. J. Gr. Cooper. Gundiaciua cau/omica. 



