PLANORBIS. 201 



above blood-heat. In the same spring were 

 some aquatic beetles [Dytiscus) and extensive 

 growth of conferva, and swimming on the sur- 

 face were two species of water birds. — W. M. 

 Gabb. 



Extra-limital. 



A. PLANORBIS FRAGILIS, Dunher. 



Plate 6, fig. 13, 14, 15. 



Shell tumid, fragile, very delicately striate, 

 pale horn or amber-colored ; deeply umbilicate 

 above, below rather concave ; whorls four, in- 

 volute, on each side rounded, rapidly increas- 

 ing, the upper ones spirally striated and decus- 

 sated, conspicuous below, aperture large, 

 spreading, oblique, kidney-shaped; lip very 

 acute, with a very delicate white callus on 

 the parietal wall. 



Diam. 12*5, alt. 6*5 mill. 



Near City of Mexico. 



I have never seen this species, which may 

 hereafter be found in Southern California. 

 (48) 



