394 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Sb». 



At any rate the distinction of species in the group of Tro- 

 pites subbullatus must be entirely artificial when one has any 

 great quantity of material. The writer has what appears to 

 be an unbroken series, grading through Ti'opites torqiiillus, 

 T. dilleri, T. subbullatus, T. fusobullatus, to T. niorloti, 

 represented, not by a few, but by a large number of speci- 

 mens of each. As these all occur in the same beds, the 

 species have no stratigraphic value, and do not mark stages 

 in evolution. 



Horizon and locality. In the Upper Trias, Karnic stage, 

 zone of Tropites subbullatus, Shasta County, California, 

 Brock Mountain, on the divide between Squaw Creek and 

 Pitt River, six miles northeast of the Bully Hill Mine, asso- 

 ciated with T. subbullatus, T. torquillus, Paratropites sellai, 

 P. dittmari, Eutomoceras sandlingense , Sagenites herbichi, 

 Trachyceras shastense, Proclydonautilus triadicus, Halobia 

 superba, and many other species. This group of Tropites 

 is common in the Tyrolian Alps in the same horizon and 

 associated with the same fauna, and probably this same 

 species occurs there too. The specific name is given in 

 honor of Mr. J. S. Diller of the United States Geological 

 Survey. 



Tropites torquillus Mojsisovics. 



Plate XLVI, Figs. 5-6; Plate XLVII, Fig. 4. 



1893. Tropites torquillus, Mojsisovics, Die Cephalopoden der Hallstatter 

 Kalke, II, p. 210, pi. ciii, figs. 1-8 ; pi. cvi, fig. 4. 



Form involute, robust, whorl high helmet-shaped, deeply embracing, and 

 deeply indented by the inner whorl. Umbilical shoulders angular with 

 nearly vertical walls. Sides curving gently from the shoulder to the venter, 

 without abdominal shoulders, so there is no separation into flanks and ven- 

 ter. The umbilicus is narrow and deep, exposing only the edge of the um- 

 bilical shoulders of the inner whorls. 



The height of the whorl is a little more than one-half the total diameter, 

 the width is about one and a half times the height, and the whorl is indented 

 to one-third of its height by the inner volution. The width of the umbilicus 

 is a little more than one-fifth of the total diameter of the shell. The surface 

 is ornamented with fine but distinct umbilical knots, from which fine dichoto- 

 mous ribs curve forward up the sides ; there are also very fine spiral lines, 

 visible only on the shell. The low central keel is not bordered by furrows. 



The septa are of the usual Tropites type, almost exactly like those of 

 Tropites subbullatus, with a divided ventral lobe, a principal lateral, and a 

 single auxiliary above the umbilical shoulders. 



