108 CARBONIFEROUS AMMONOIDS OF AMERICA. 



the total diameter. Umbilical shoulder abruptly I'ounded and ornamented 

 with fine nodes or ribs. 



Septa lanceolate, lobes pointed and ling-upeform, saddles rounded. 

 Ventral saddle long-, narrow, and bottle-shaped; ventral lobes long, tongue- 

 shaped; three lateral lobes, similiar in shape, but decreasing in size toward 

 the umbilicus. 



This species is most nearly related to <S'. hiiatt'i Smith, but has a wider 

 umbilicus, more globose whorls, and retains the umbilical ribs to a greater 

 size. It is quite possible that <S'. lnjatti may be only a variety of *S'. hiJdrethi, 

 but they will be kept separate until enough s])ecimens are found to show 

 the intergradation. 



Hang" redescribed S. hildretJii and assigned to it the genus Af/athiceras, 

 at the same time stating that it did not agree entirely with the type of 

 Agathiceras ; but Hyatt's genus Schistocenis was unknown to him, since it had 

 not been figured and the type species had not been named. 



Occurrence. — Upper Coal Measures (" Lower Barren"), near Candiridge, 

 Guernsey County, Ohio, and Cisco formation, Graham, Young County, Tex. 



Specimens are in the U. S. National .Museum from Graham, and liaug 

 has rediscovered one in the Verneuil collection of the Ecole des Mines, 

 Paris, presented by Hildreth, from Cambridge, Ohio. 



SCHISTOCERAS HYATTI Smith, Sp. UOV. 



PI. XX, figs. 1-8; PI. XXI, figs. 10-13. 



1884. Schistoceraii, sp. indct., A. Hyatt. Proc. Boston Hoc. Nat. Hist., Vol. XXII, p. 336. 



Form somewhat compressed laterally, with liigh helmet-shaped whorl, 

 sloping sides, rounded venter, rounded umbilical shoulders, and deep, open 

 umbilicus, showing the inner whorls. The last whorl is indented to two- 

 fifths of its height by the preceding whorl. No ribs or constriction occur 

 on the mature shell, but the surface is ornamented with fine spiral strijie 

 and fine siimous cross stria>, giving a beautifully reticulated appearance to 

 the shell. In tlie adolescent stages there are strong umbilical ribs, which 

 become obsolete at a diameter of about 15 nun. The septa are goniatitic, 

 but complex, divided into a large number of lobes and saddles. The 

 siphonal saddle is long, notched, and bottle-shaped; the three lateral 



o Etudes BUT les Goniatites, p. 105. 



