132 CARBONIFEROrS AMMONOIDS OF AMERICA. 



Genus PoPANOCERAs Hyatt. 



This geiiu8 was established by H3'att" to include involute, slightly 

 compi'essed forms, with almost closed umbilicus and little sculpture. The 

 saddles are rounded and entire; the external lobes, four or more in number 

 on each side, are serrated, either bifid or trifid. 



The type is Goniafifes ]:inf/ianus M. V. K., from the Artinsk beds of the 

 Permian of the Ural Mountains. Several Triassic species have usually 

 been classed under this group, but they are now placed under Parapopa- 

 noceras Haiig, which differs from Popanoceras in having the lobes distinctly 

 serrated, with the denticulations encroaching on the saddles. 



Popanoceras ganti Smith, sp. nov. 



PI. XXT, figs. 14-lG. 



This species is involute, with broadly rounded venter and slightly flat- 

 tened sides, very involute and close-coiled, with umbilicus almost closed. 

 The shell has fine cross lines of growth, slightly curved forward, and five 

 sharply defined, backward-cnrving constrictions on the last whorl, parallel 

 to the cross stria^. The septa are tyjMcal of Popanoceras^ and are divided 

 into numerous lobes and saddles. The external lobes are five in number 

 on each side, and the intei'ual are five on each side, with an undivided 

 autisiphonal. The saddles are all i-ounded and entire, the lobes all 

 denticulate. The external lobe is short and bifid, the lateral lobes all trifid. 

 The siphonal saddle is notched by a shallow indentation. The shape and 

 number of the internal lobes could be seen, but it could not be ascertained 

 whether or not they are denticulate. 



Affinities. — Popanoceras ganti resembles slightly P. parkeri Heilprin, but 

 differs from it in being somewhat more compressed laterally in the shorter 

 lobes and saddles, and in having the first lateral lobe trifid instead of 

 bifid. It is thus a more specialized form than P. parkeri, but simpler than 

 P. walcott) White of the Permian, from whicli form it differs in the smaller 

 numl:)er and greater simplicit}' of its lobes. It may possibly be an inter- 

 mediate form iu the genetic series of P. parkeri and P. walcotti. This 



f'Proc. Boston 8oi-. Nat. Hist., Vol. XXII, p. ;«7. 



