156 



NORTH AMERICAN INDEX FOSSILS. 



CV. Celtites Mojsisovics. 



Evolute, slightly embracing, ceratitoid shells, with low whorls in- 

 creasing very slowly in height, and of quadratic section; sides 

 flattened; ventral shoulders abruptly rounded, venter flattened; 

 surface with simple ribs becoming obsolete at shoulder ; suture 

 goniatitic or slightly serrated. Triassic. 



250. C. halli Mojsisovics. (Fig. 1404, J-/.) 



Outer whorl concealing about one third of preceding one ; ribs 



Fig. 1404. a-c, Longoba7-dites nevadanns, two views X /^> ^"^ suture enlarged; 

 d-f, Celtites halli, two views X /^» ^"<i suture enlarged ; g-j, Colu??ibites pariiianus, 

 two views of adult X K' ^ inner whorls, and 7, suture, enlarged. (See p. 160.) 

 (After Hyatt and Smith. ) 



becoming obsolete at point of involution ; suture with a divided 

 ventral, and two small laterals ; first lateral serrated. 

 Middle Triassic of West Humboldt Range, Nevada. 



CVI. TiROLiTES Mojsisovics. 



Evolute ceratites, robust, laterally compressed, and with flattened 

 or gently rounded venter, and square abdominal shoulders against 

 which the simple ribs end in spines ; suture with divided, external 

 lobe and serrated first lateral. In Metatirolites, a distinct auxiliary 

 lobe occurs on the umbilical shoulder. Triassic. 



