LOWER CALIFORNIAN MOLLUSCA. 34I 



some differences exist, they are not so great as those 

 seen in the subspecies of B. inscendcns here given. 



Helix areolata exanimata J, G. C. Plate xiv, fig. 7. 

 Same reference, p. 216. 



Planorbis (Anisus) anitensis n. sp. Plate xiv, fig, 8. 



Shell (when held mouth downward) with the right side 

 concavo-convex, the left flat (or slightly concave), the 

 left margin forming a sharp carina expanded beyond the 

 solid edge of shell, which is marked by a compressed 

 line. Whorls 5, visible on both sides, uniformly flat on 

 the left side, forming a concave umbilicus on the right, 

 where their surface is rounded. Mouth triangular, the 

 right lip arched, the left nearly flat, the extremities joined 

 to outer angle and to obtuse margin of umbilical cavity. 

 Umbilicus half as wide as the shell; flat side of mouth 

 one-fourth of diameter; greatest breadth (at mouth) over 

 one-fifth of same; greater diameter 0.26, least 0.03 inch. 



Habitat. — Four specimens found in a laguna at Santa 

 Anita, Lower California, at an elevation of 100 feet, and 

 10 miles from San Jose del Cabo, Lower California. 



This species seerns to come nearest to some of those 

 of tropical America, as P. kennatodes Orbigny, which 

 differs in larger size, etc. It approaches also to P. 

 -planorbis Linne {niai'ginatiis Drap.) and P. nitidusMul- 

 ler of Europe, but none seem to be so much flattened 

 or doubly concave. The only similar North American 

 species is P. exacutus Say, which also differs in being 

 lenticular in form (or doubly convex in outline). That 

 species is also unknown nearer than Vancouver Island 

 and Kansas, 2,000 and 1,000 miles distant. A compari- 

 son of this shell with P. (Menettis) opcrcularis Gould, 

 shows that it is reversed, the flattened side beino- the 

 right in that shell, which Dr. Gould describes ; al. 



2d Ser. Vol. III. ( 25 ) 3. 



