SCHISTOCERAS. ' 111 



A still larger specimen (one of Hyatt's types) is shown on PI. XX, figs. 

 6 and 6, giving the following dimensions: 



Millimeters. 



Diameter 42 



Height of last whorl 20. 5 



Heifiht of last wlun'l from the preceding 14 



AVidth of la.«t whorl 21 



Width of umbilicus 9. 5 



Involution 6. 5 



The largest specimen fignred, diameter 69 nnn., showed about two-thirds 

 of a revolution more than the last, but no change in septa, shape, or sur- 

 face characters (PI. XX, figs. 7 and 8; PI. XXI, fig. 13). Thus Schistoceras 

 clearly is derived from Gastrioceras, through Paralegoceras, and undoubtedly 

 belongs to the Glyphioceratidse, being the most complex member of that 

 group. 



Schistoceras missoukiense Miller and Faber. 



PI. VIII, fig. 1. 



1892. Goniatifes missourtensis. Miller and Faijcr, Jour. Cincinnati Soc. Nat. Hist., 

 Vol. XIV, p. 16-4, PL VI, fig. 1. 



Shell subglobose, involute, whoi'ls highly arched, helmet-shaped, sides 

 somewhat flattened, about twice as high as broad, deeply embracing, show- 

 ing but little of the inner whorls, and deeply indented by them. Umbilical 

 shoulders abruj^t ;uid the umbilicus is deep and rather narrow, being hardly 

 one-fourth of the total diameter. Surface apparently smooth, no constric- 

 tions being visible. The preservation of the cast does not permit the 

 determination of the presence or absence of umbilical ribs. 



Septa consisting of four lateral lanceolate lobes on each side, and 

 probabl}' a fifth on the umbilical border. The saddles are also like the lobes, 

 but more constricted and club-shaped. The form and sejjta are unmistak- 

 ably those of Schistoceras, and the species may very likely be identical 

 with either >§. hyatti or S. hildretJii, but the figures and description of S. mis- 

 soiiriense do not permit this determination. It seems to be more compressed 

 and to have a narrower lunbilicus than either of the other s])ecies. 



Occurrence. — Upper Coal Measures, Missouriau stage, llnish Creek, near 

 Kansas City, Mo. Type in paleontologic collection. Walker Museum, 

 University of Chicago. 



