18%.] ZbJ [Smith. 



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

 arate the species, exceeding by one the number on the sides of G. globu- 

 losiim. 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 Glyphioceras sphmriciim Martin. As many as six whorls are 

 known. 



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

 the Glyphioceratida', 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 

 tw^o 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. 



The septa are exactly like those figured by Meek and Worthen, so 

 that no further description of them is necessary ; they are typical of tlie 

 genus Gastrioceras, as characterized by Hyatt, although, as Karpinsky* 

 remarks, the sutures alone are not sufficient to separate the genera Gly- 

 phioceras, and Gastrioceras, since a comparison of the sutures of Gastri- 

 oceras jossm Verneul and Glyphioceras diadema Verneul (not Goldfuss) 

 shows the almost perfect similarity of the two. 



The surface of the shell was unknown to Meek and Worthen, but 

 some of the Arkansas specimens have the shell partially preserved. It 

 is marked with fine, sharp, doubly arcuate, sickle-shaped stri* or ribs, 

 with the sinus on the ventral portion pointing backwards. This surface 

 ornamentation resembles that of Glyphioceras ohtusuin Pliillips, Geol. of 

 Yorkshire, ii, p. 285, PI. xix, Figs. 10-13, but the form is much more 

 globose, and the lobes unlike those of Phillips' species. 



Dimensions. — One of tlie fragments shows a diameter of over two 

 inches ; on this onlj' the body whorl was seen, it being at least one coil 

 in length. 



Bi/iicnsions of the Largest Figured Specimen. 



MM. 



Diameter 36 



Breadth 27 



Height of last whorl 14 



*"Ueber die Ammoneen der Artinsk-Stufe," Man. Ac. Inper. Sci. St. Petersburg, vi 

 Series, Tome xxxvii, No. 2, p. 46. 



