296 PROCEEDINGS OF THE ACADEMY OF [1889. 



Straparollus obtusus (Hall). 



Euomphalus obtusus Hall, 1858. Geol. Iowa, vol. I, p. 523. 



Shell large, planorbiform, composed of five to six regularly 

 rounded volutions; spire on a level with, or slightly below, the 

 upper surface of the last whorl; suture very deeply impressed; 

 upper face of the volutions very slightly flattened on the inner side 

 near the suture; umbilicus very broad and shallow; aperture 

 circular. 



This form was the first of the group recognized from the neighbor- 

 hood of Burlington, and is the most characteristic gasteropod of the 

 Kinderhook at that place. It occurs in the oolitic layer a few feet 

 below the Burlington limestone, and is easily distinguished from 

 all the congeneric species of the locality by its large size — often 

 having a diametric measurement of six centimeters, — its greatly de- 

 pressed spire, broad shallow umbilicus and regularly rounded 

 whorls. In many examples of this species the volutions are barely 

 in contact with one another, and in a few instances the outer whorl, 

 toward the aperture, has actually become separated from the 

 adjoining inner turns. This fact is of special interest as illustrating 

 the first noticeable departure toward certain evolute Straporolli 

 which have been referred to Phanerotinus of Sowerhy. 



From the associated beds Winchell has described a gutta-percha 

 cast, taken from natural moulds in friable sandstone, as Phanerotinus 

 paradoxus. One of the specimens figured by Hflll (Pake. N. Y., V, 

 ii, pi. 16, fig. 16), shows the inner volutions still contiguous, while the 

 outer whorls are not separated further than very similar casts of un- 

 doubted S. obtusus. 



Sphaerodoma pinguis (Winchell). 



Macrochilus pingue Winchell, 1863. Proc. Acad. Nat. Sci. Phila., 

 p. 21. 



The specimens which evidently represent the group formerly 

 known as Macrochilus are merely imperfect casts from the arenaceous 

 beds of the Kinderhook, and their systematic position can at best 

 only be surmised. But unsatisfactory as the material is, it is of con- 

 siderable interest to find in America the genus present so early in 

 the Carbonic. Several American Devonic forms have been described 

 under Macrochilus, but with perhaps one or two exceptions, they 

 have been very imperfect and in most cases merely internal casts. In 

 Europe, however, Macrochilus is equally well represented in the 



