Geol— Vol. I.] SMITH— COMPARATIVE STRATIGRAPHY. 389 



the center, giving a resemblance to Proti'achyceras. The 

 septa are usually ceratitic,the saddles being mostly rounded 

 and entire. The ribs and spines are like those of Trachy- 

 ceras s. str. and Protrachyceras. 



This subgenus ranges from the upper Muschelkalk to the 

 middle of the Upper Trias. In America it is known only 

 in the upper part of the Middle Trias of Nevada, where it 

 is represented by T. whitneyi G^Mh, T. w^e-^/ Mojsisovics, 

 T. hyatti Smith, sp. nov., and by several undescribed 

 species. 



Trachyceras (Anolcites) hyatti Smith, sp. nov. 



Plate XLIII, Fig. 12; Plate XLV, Figs. 1-2. 



Evolute, whorls robust, little embracing, and little indented by the inner 

 whorls. Cross-section quadratic, a little higher than wide. Venter broad 

 and flat. Umbilical shoulders abruptly rounded, ventral shoulders square. 

 Sides convex. Umbilicus very wide. The sculpture is rugose; coarse ribs 

 start out from the umbilicus, and the alternate ones bifurcate at lateral spines 

 halfway up the sides, the two branches ending in strong spines on the ven- 

 tral shoulders. These shoulder knots alternate on the two sides, and are 

 continued in ridges diagonally across the venter. There is no ventral furrow, 

 but the marginal knots are higher than the flattened space. 



In youth there are strong umbilical knots, but with increasing age these 

 move up the sides as far as the middle, becoming the lateral knots where the 

 ribs branch. 



Anolcites hyatti is very closely allied to A. whitneyi 

 Gabb^ but differs from Gabb's species in being more 

 evolute, and in having coarser sculpture and stronger 

 spines. In A. whitneyi the whorl is more flattened, and 

 the angle below the shoulders is less pronounced. The 

 adolescent shells of A . hyatti are more involute and have a 

 broader whorl than those oi A. ivhitneyi, and the ribs are 

 fewer in adolescence as well as at maturity. 



The young stages are very similar to Ceratites altecostatus 

 Arthaber^, and show a transition from Ceratites X.o Anol- 

 cites. F. von Hauer has described a species, Ceratites 



> See Bibliog. 9-p. 23, pi. iv, fig. 11 (not 12 and 13), which is Protrachyceras amcricanum 

 Mojsisovics. 



*See Bibliog. i— p. 59, pi. v, figs. 7 a-d. 



