GASTKI0CEKA8. 89 



the University of Chicago, for the opportunity of studying the specimen, 

 and for the photographs of it. On PI. XVI, tigs. 2a and 2b, is figured a 

 specimen from the ^Middle Coal Measures of Pope County, Ark., T. 10 N., 

 R. 20 W., sec. 8, collected by the geological survey of Arkansas, and 

 now deposited at Leland Stanford Junior University. 



Gastrioceras globulosum Meek and Worthen. 



PI. VI, fig. 1; PI. XXI, figs. 7-9. 



IcStit). (roniatites (jIohuIosKS, Meek and Worthen, Proc. Acad. Nat. Sci. Phila.. 1860, 



p. 471." 

 1866. Goniatites fflohdosus, Meek and Worthen, (tpoI. Surv. Illinois, Vol. ]I, p. 390. 



PI. XXX, tig. y. 

 ISSJr. Gastrioceras globa/osNh^.A.YiyiM, Proc. Boston Soc. Nat. Hi8t.Vol.,XXII, p. 



327. 

 1896. Gastrioceras glohdosum, J. P. Smith. Proc. Am. Philos. Soc, Vol. XXXV, 



p. 258, PI. XVIII, tigs. 1-6. 

 1898. GlypMoceras globulosum, E. Haug, Etudes snr les Goniatites, p. 26. 



This species has some slight resemblance to Paralegoceras haylorense of 

 the Texas Permian, but the lobes of the latter are alone sufficient to separate 

 the species, exceeding by one the number on the sides of G. globulosum. 

 The Texas species also has the umbilicus much wider and more open, and 

 is not so globose. 



The angle of the umbilicus is 45°, which remains constant notwith- 

 standing the fact that the shell grows more involute with age, being in its 

 youth a comparatively open coil. In youth the whorls are flattened, but 

 with age they become more rounded, until the shell reaches almost the form 

 of Goniatites sjfhcericns ]\Iartin. As many as six whorls are known. 



The deeply marked constrictions, that are so common in the family of 

 the Glyphioceratidpe, are seen on the casts, about four to a whorl. 



Sutures. — The sutures show nine lobes and nine saddles; the siphonal 

 lobes are narrow and pointed, the first lateral lobe is broad, but pointed, 

 and on the umbilical shoulder is a small, pointed "suspensive" lobe. There 

 are three pointed, internal (concealed by the involution) lobes, of which 

 the antisiphonal (dorsal) is the longer. 



The siphonal saddle is rather deeply notched, long and narrow; the 

 two lateral saddles are broad and rounded. The two internal saddles are 

 rather pointed and long, as is the case with most species of this genus. The 

 internal lobes and saddles have never been seen before in this species. 



