GASTROPODA— MELANIIDJE. 



74 1 



shelf due to prominence of spiral. Five strong spirals, of which 

 the upper three appear on all whorls. Faint vertical sculpture 

 between these. Aperture ovoid. 



Fresh-water Miocenic of Idado, Nevada. 



452. M. taylori Gabb. (Fig. 1076, £\) Miocenic. 

 High-spired with three strong spires visible on all whorls, suture 



impressed, vertical sculpture moderate between spirals ; aperture 

 oval. 



Fresh-water Miocenic of Idaho. 



CXXVIII. Melanopsis Lamarck. 

 Shell generally shorter and thicker than Melania, with aperture 

 bearing strong basal notch and with inner lip callous. Surface 

 smooth or ornamented as in Melania. Cretacic-Recent. 



453. M. americana White. (Fig. 1076, h, i.) Cretacic. 

 Small, sutures not impressed, whorls flattened, shell gently 



tapering from middle of body whorl ; canal short, slightly reflexed ; 

 surface smooth. 



Laramie of Colorado. 



CXXIX. Pyrgulifera Meek. 

 Thick, elongate, oval shells, whorls with narrow shoulder 

 bounded by strong angulation on which the ribs are produced as 



Fig. 1077. Pyrgulifera Aumerosa, opposite views of two specimens showing varia- 

 tion. (U. S. G. S.) 



spinose tubercles ; spirals numerous but subdued, aperture oval, 

 sometimes with very faint canal. Cretacic. 



454. P. humerosa Meek. (Fig. 1077, a-d.) Cretacic. 



Shoulder concave, tubercles strong, blunt, and produced down- 



