l62 



NORTH AMERICAN INDEX FOSSILS. 



262. D. sandlingerensis Haiier. (Fig. 1409, c?, ^.) Triassic. 



Ribs single or dichotomous ; sides flat, outer whorl one half 

 diameter of shell ; keel high and hollow. 



Upper Triassic of Shasta County, California, also common in 

 Alps. 



CXV. Paratropites Mojsisovics. 



Less compressed than preceding, with rounded ventral shoulders 

 and sunken keel. Triassic. 



263. P. sellai Mojsisovics. (Fig. 1409, /-/?.) 



Triassic. 



Fig. 1409. a-c, Tropites subbu/iatus, X /^» ^"d suture ; d, e, Discotropites sand- 

 lingerensis, side views and suture X M ' f~^i Paratropites sellai, two views and suture 

 X Yz- (After Hyatt and Smith.) 



Ribs begin in bundles, and curve abruptly forward over ventral 

 margins, usually dichotomous ; keel low, bounded by narrow 

 grooves. 



Upper Triassic (Karnic) of California (Hosselkus). 



Arcestida. 



CXVI. Arcestes Suess. 



Globose or subglobose, involute and deeply embracing shells, with 

 closed umbilicus; body chamber longer than last volution, often 

 contracted and differing in shape from other whorls ; whorls 



