392 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 30 Ser. 



and fewer. It differs from Trachyceras attila MojsisovicsS 

 in being less robust, and in finer sculpture, also in the 

 somewhat more complex lobes. 



Horizon and locality. Upper Trias, Karnic stage, zone 

 of Tropites subbullatus, Shasta County, California, Brock 

 Mountain, on trail from Squaw Creek to Pitt River, six 

 miles northeast of the Bully Hill Mine; associated with 

 Tropites suhbiillatus, Paratroj[)ites sellai, Proclydonautilus 

 triadicus, Halobia superba, etc. 



Genus Tropites Mojsisovics. 



1875. Tropites (pars), Mojsisovics, in M. Neumayr, Die Ammoniten der 



Kreide, und die Systematik der Ammonitiden. Zeitschr. Deutsch. 



Geol. Gesell., 1875, p. 889. 

 1879. Tropites (pars), Mojsisovics, Vorlaufige kurze Uebersicht der 



Ammoniten-Gattungen der Mediterranen und Juvavischen Trias, 



p. 136, 

 1893. Tropites (pars), Mojsisovics, Cephalopoden der Hallstatter Kalke, II, 



p. 184. 

 1896. Tropites (pars), Mojsisovics, Beitr. Kennt. Obertriadischen Cephalo- 



poden-Faunen des Himalaya, p. 39. 



Type, Ammonites subbullatus Hauer. 



Generic characters: Moderately evolute whorls, not deeply embracing, and 

 not deeply indented by the inner volution. Umbilicus open, and deep, with 

 steep inner walls. Whorls usually broader than high, with angular prominent 

 umbilical shoulders, and arched venter that may be either broad and low, or 

 helmet-shaped. At maturity the whorls are often contracted, showing egres- 

 sion, so that the body-whorl is lower and narrower than the inner volutions. 

 The cross-section is usually trapezoidal, and in the typical forms there are no 

 flanks, for the venter is so flattened that it begins at the umbilical shoulders. 

 Surface ornamented with strong umbilical knots, from which dichotomous 

 start out curving gently across the sides to near the middle of the venter, 

 upon which a strong keel is developed, usually with marginal furrows at 

 which the ribs end. The surface of the shell has also spiral lines, which are 

 not visible on the cast. No constrictions appear on the shell, and no knots 

 except on the umbilical shoulders. The body-chamber is very long, more 

 than a complete revolution. 



The septa are ammonitic, but not deeply digitate, the number of the lobes 

 varying with the shape of the whorl, but always of the dolichophyllic type. 



Tropites is confined to the Karnic and Noric stages of 

 the Upper Trias, in which horizons it occurs in the Alps, 



1 See Bibliog. 23— II, p. 633, pi. clxix, figs. 6-9; pi. clxx, figs. 1-2. 



