AGATlllCEKAS. 131 



Agathiceras ciscoense Smith, «i). nov. 

 PI. XXI, %s. 17-19. 



In the U. S. Natioiiul Museum is deposited a specimen that meets all 

 the requirements of the genus Af/athiceras, the type of A. ciscoense sp. nov. 



This species is rather high-whorled, with rounded venter and flattened 

 sides. The umbilicus is closed, and thus narrower than in I'aralcffoceras 

 and Schistoceras. The surface has constrictions, and is ornamented witli very 

 strong spiral lines or ridges narrower than the intermediate furrows, as 

 in European species of this genus. It, however, lacks the network of fine 

 cross lines of growth seen on Schistoceras, and this difference may turn out 

 to be one of the criteria for the separation of the two genera. 



The septa resemble those of Schistoceras in number arid general shape, 

 but the lobes are rounded and not pointed. The siphonal saddle is 

 notched. The four lateral saddles are rounded and entire, s})atulate in 

 shape, while the four external lobes are constricted and tongue shaped. 



This species resembles A. siiessi Gemmellaro, of the Permian Fusulina 

 limestone of Sicily, but is slightly more compressed. This difference might 

 not be more than individual if the association and range of the two were 

 the same, but in view of the great separation and differences in faunal 

 association it must be specific. A. uralicum occurs in the Upper Carbon- 

 iferous limestone of the Ural Mountains, but does not resemble A. ciscoense 

 except in a general way. 



Occurrence. — In the Upper Coal Measures, Cisco formation, of Graham, 

 Young County, Tex., associated with a t3q3ical Missouriau fauna. Only 

 a single specimen is known, deposited in the U. S. National Museiim 

 (No. 27199), collected by A. B. Gant. 



Dimensions of the specimen figured: 



Millimeters. 



Diameter 35 



Height of last wliorl 19 



Heiglit of Iaf*t whiorl from the preceding 12 



Width of last whorl 14 



Involution 7 



Width of umbilicus (dosed) 



