Permo-Carboniferous Ammonoids of the Glass Mountains 131 



ferent from ours. Much more similar is the suture of Stacheoceras 

 Trimurti Dien./ which also shows a bifid first lateral lobe in the 

 younger stages and one ending in four points in older specimens ; but 

 the form of this latter species is entirely different from that of St. 

 Bowmani. 



A little more similar in general form is Stacheoceras Walcotti 

 White^ but the ornamentation is different and the suture line shows 

 only trifid lobes (even on the branches of the siphonal lobe) and thus 

 to a certain degree resembles Stacheoceras tridens Rothpl.^ 



Age: 



Word formation, Permo-Carboniferous. 



Number of specimens examined: 



Twelve. The species is not very rare at the principal localities. 



Locality: 



Junction of Road and Gilliam Canyons and the mountains near it ; 

 also on the mountain north of Leonard Mountain, Glass Mountains. 



Stacheoceras gilliamense nov. sp. 

 PL VI, Fig. 70-76 



Shell small, globose, with rounded flanks and ventral part ; very in- 

 volute, composed of deeply embracing whorls. The greatest width is 

 on the umbilical shoulder. The whorls are much broader than high 

 and of a semilunar cross-section. The umbilicus is narrow and deep, 

 the umbilical wall is nearly vertical and relatively broad, but slightly 

 curved. No constrictions and no ornamentations are visible although 

 the shell is preserved. 



The sutural line is not entirely known. What is visible on the ex- 

 ternal surface turns out to be the internal suture of the next whorl. 

 We have shown in the descriptions of our Agathiceras Girtyi n. sp. 

 that this case is quite frequent in the same zone. The fossils are sirfci- 

 fied throughout, and the inner side of one whorl is pressed so closely 



'Diener, Permocarb. fauna of Chitichun No. 1, p. 10, pi. 1, fig. 1-af. 



^Ch. A. White, The Texan Permian, etc., p. 21, pi. 1, fig. 9-11. 



"Rothpletz, Perm., Trias., und Jura auf Timor u. Rotti, p. 87, pi. 9, fig. 4. 



