384 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



even in the Permian. The latter genus is usually classed 

 with the Leiostraca, but this artificial classification can not 

 separate groups that are manifestly closely allied. 



As to the more remote ancestor of Ceratites, all species 

 of this group go through a stage resembling Tirolites, 

 which is probably the primitive radicle not only of Ceratites, 

 but also of the entire family of the Ceratitidae. This 

 group has usually been regarded as an offshoot of the gon- 

 iatite family Glyphioceratid^, to which, however, the young 

 of Ceratites have no resemblance. The typical members of 

 the Ceratitidae, in their adolescent and late larval stages, 

 resemble the Prolecanitidae, and probably are connected 

 with that group through Paralecanites. 



Ceratites is characteristic of the Middle Trias of the 

 Mediterranean, Oriental, Arctic, and American regions, 

 but in India and Siberia is found also in the upper part of the 

 Lower Trias. And it has also been described by Mojsiso- 

 vics from the Upper Trias of the Alpine province, although 

 the forms ascribed to Ceratites are very different from the 

 original type of the Nodosi and are probably not congen- 

 eric with it. The genus is represented in Nevada by 

 about thirty species belonging partly to the group of Cera- 

 tites nodosi partly to Ceratites geminati, and partly to Cera- 

 tites -polaris. 



Ceratites vogdesi Smith, sp. no v. 



Plate XLIII, Figs. 7-8; Plate XLIV, Fig. i. 



Form evolute, robust, whorls subquadratic, a little higher than wide, with 

 rather broad venter raised in the middle to a low central ridge, and with 

 abrupt subangular ventral shoulders. The umbilicus is rather wide and deep, 

 with abruptly rounded umbilical shoulders. The outer whorl conceals more 

 than one-half of the inner, and is indented by it to about one-half of the 

 height. The width of the whorl is about four-fifths of the height, and the 

 height is about three-sevenths of the total diameter. The width of the 

 umbilicus is one-third of the total diameter. 



The surface is ornamented with coarse, radial ribs that start out from the 

 umbilical shoulders, develop strong spines about two-thirds of the way up 

 the flanks, and again on the abdominal shoulders. There are eight of the 

 principal ribs and lateral knots to a revolution, and twice as many spines on 

 the shoulders. The intermediate ribs are fainter and do not develop spines. 



