88 University of Texas Bulletin 



Diameter of 

 umbilicus 

 (between 

 umb il ieal 

 shoulders. . .? 7.7 0.29 3.9 0.34 3.0 0.34 2.4 0.39 



Relation to other species : 



Our species belongs without doubt to the group of G. Zitteli Gemm.' 

 but is certainly much less evolute. It resembles, perhaps still more 

 Gastrioceras sosiense Gemm.^ but also in this species the umbilicus is 

 relatively larger while the transversal ribs at the umbilical shoulder are 

 shorter and less conspicuous. 



None of the Gastrioceras from the Russian Artinsk is very similar 

 to our species, G. Jossae Vern.^ being much more evolute; while G. 

 Suessi Karp.* lacks the strong transversal ribs on the umbilical shoul- 

 der. The other species of Gastrioceras of the Artinsk apparently be- 

 long to entirely different groups. 



None of the carboniferous Gastrioceras much resembles our species. 

 Much more similar than any other one is perhaps G. altudense n. sp., 

 but it has a smaller number of spiral ribs and the umbilical ribs are quite 

 different.' 



Age: 



Word formation, Permo-Carboniferous 



Number of specimens examined : 



Ten. The species is by no means very rare, but generally not very 

 easy to collect. 



Locality : 



Junction of Road and Gilliam Canyons ; hill north of Leonard Moun- 

 tain, Glass Mountains. 



Gastrioceras altudense n. sp. 

 PI. III. Fig. 1-6 

 Shell discoidal, evolute, compressed on the flanks, rounded on the 

 ventral i-egion; cross-section parabolical, greatest width at the um- 



'Gemmellaro, Calc. c, Fusulina, p. 85, pi. 6, flg. 18-20; pi. 7, fig. 17. 

 ^Gemmellaro, loc. cit., p. 88, pi. 7, fig. 17-19. 

 sVerneuil, G6ol. de la Russle, II, p. 370, pi. 26, fig. 2 (not 3). 

 *Verneuil, G6ol. de la Russie, II, p. 371, pi. 26, flg. 3. 

 Karpinsky, Amm. d. Artinsk-?tufe, p. 52; pi. 3, flg. 3. 



