Geol.— Vol. I.] SMITH— COMPARATIVE STRATIGRAPHY. 397 



marginal furrows. The umbilicus is narrow, almost closed at early maturity, 

 but becoming slightly wider with increasing age. The surface is ornamented 

 with straight ribs on the flanks, bending forward abruptly on the abdominal 

 shoulders. These ribs bifurcate near the umbilicus and again higher up on 

 the flanks in an irregular manner. Th^re are no umbilical knots at maturity, 

 or only very faint rudiments of them. 



The septa are ammonitic, of the usual type of the Tropitidae. The height 

 of the whorl is about one-half the total diameter of the shell, and the width 

 is two-thirds of the height. The whorl is indented to one-half its height by 

 the inner volution, and conceals nearly all of the inner volution, except the 

 umbilical border. The umbilicus is about one-seventh of the total diameter 

 of the shell. 



Paratrofites dittmari is closely allied to P. sellai Mojsiso- 

 vics, with which it is associated in both the Alpine province 

 and in California ; it differs from that species in the more 

 compressed whorl, in the fewer and flatter ribs, and the 

 obsolescence of the umbilical knots. These same charac- 

 ters serve also to distinguish it from T. saturnus Dittmar, 

 on which also the lateral ribs are not straight, but curved 

 broadly forward on the flanks. 



Horizon and locality. Upper Trias, Karnic stage, zone 

 of Tro^ites suhbullatus, Shasta County, California, Brock 

 Mountain, on divide between Squaw Creek and Pitt River, 

 six miles northeast of the Bully Hill Mine. In the Tyrolian 

 Alps it was found in the same horizon, and associated with 

 the same fauna. 



Eutomoceras sandlingense Hauer. 



Plate XLVI, Fig. 10; Plate XLVIII, Figs. 5-6. 



1849. Ammonites sandtingensis Hauer, Ueber neue Cephalopoden aus den 

 Marmorschichten von Hallstatt und Aussee. Haidinger's Naturw. 

 Abhandl. Bd. Ill, p. 10, pi. iii, figs. 10-12. 



1866. Ammonites sandtingensis Dittmar, Zur Fauna der Hallstatter Kaike, 



P- 370- 

 1893. Eutomoceras sandlingense Mojsisovics, Cephalopoden der Hallstatter 

 Kalke, Bd. H, p. 285, pi. cxxx, figs. 11-13, pi. cxxxi, figs. i-ii. 



Involute, laterally compressed, discoidal, deeply embracing whorls, deeply 

 impressed by the inner volutions. Umbilicus narrow, about one-eighth of 

 the diameter of the shell, but exposing the umbilical shoulders of the inner 

 whorls. Umbilical shoulders abruptly rounded. Sides flattened-convex, 

 curving gently to the acute venter, with hardly any abdominal shoulders. 

 Venter acute, narrow, surmounted by a high hollow keel, which is thinner at 



