Smith.] -^"4: [Oct. 2, 



The Arkansas specimen is a septate east that when complete must 

 have heen at least four inches in diameter. The whorl is broader and 

 rounder than on the Iowa specimen, but this is to be expected on a 

 young individual since the evolution of most of these forms takes place 

 after this manner. The whorls are quite Involute and the umbilicus is 

 narrow on the young shell, becoming wider as the shell grows older. 

 The surface of the cast is smooth, no constrictions or other ornamenta- 

 tions appearing on the older shell. But on the younger shell the um- 

 bilical shoulders show faint ribs, that shade off into tine undulations on 

 the sides. Hyatt has shown the same thing in Geol. Survey Texas, Sec- 

 ond Ann. Beiiort, p. 355. But in Texas specimen the ribs persist to a 

 much later stage than on that from Arkansas. 



Dimensions. — Although the specimen was not well preserved, the 

 measurements of the entire form could be taken. They were as follows : 



MM. 



Diameter 55.5 



Height of last whorl from umbilicus 25.5 



Height of last whorl from top of inner whorl 17.0 



Width of umbilicus 13.5 



An inner coil taken out of the same specimen gave the following 

 measurements : 



JIM. 



Diameter 28.5 



Height of last whorl from umbilicus 12.0 



Height of last whorl from toji of inner whorl 7.5 



Width of umbilicus 0.0 



These show the inner coils to be much lower, less highly arched, and 

 less embracing than the outer ones. 



Surface Markings. — On the inner whorls a trace of the shell is pre- 

 served, and is like that figured by Hyatt. The undulating stria' are like 

 those common on the Glyp/iioceratida'. 



Sutures. — The sutures are like those figured by Meek and W^orthen, 

 but the siphonal saddle is notched by a small siphonal lobe. The three 

 external lateral saddles are broadly rounded, while the lobes are sharply 

 pointed. The lobes are eleven in number, three on each side, one on 

 each umbilical shoulder (suspensive lobe) and three internal, that is, 

 covered by the involution. The interior lateral lobes and the antisiph- 

 onal lobe (dorsal; are very sharp and long. These have not been seen 

 before on this species. The sutures approach very closely to those of 

 Gastrioccras russiense Zwetajew, but Paralegoceras ioicenseh^s, one more 

 pair of lobes than the Russian species and has also a suspensive lobe on 

 the umbilical shoulders. In the latter characteristic Paralegoceras 

 iowense resembles P. tschernyschcici Karpinsky (Ammoneen der Artinsk- 

 Stufe, p. 62, PI. iii. Fig. 1). Karpinsky {loc. cit.), has emended Hyatt's 



