GASTROPODA. 117 



Class GASTROPODA 



SUBCLASS STREPTONEURA 



Order Aspidobranchia 



Suborder Docoglossa 



Family Bellerophontidae 



Genus Bellerophon Montfort 



Bellerophon sp. 



Plate 27, figures 2 and 3; plate 30, figure 9 



Bellerophon is represented by only one mould from the Mineola and by several 

 small specimens from the Snyder Creek. The specimens are too imperfect to warrant 

 specific identification. Savage identifies specimens from the Grand Tower of Illinois 

 as B. pelops Hall. The specimen from the Mineola agrees with B. pelops in shape. 



Suborder Rhipidoglossa 



Family Pleurotomariidae 



Genus Pleurotomaria Sowerby 



Pleurotomaria sp. undet. 

 Plate 28, figure 2 



A large gastropod too imperfect for specific determination. The shell is preserved 

 only on a small part of the outer side of the body whorl. It is not possible to determine 

 whether a slit was present. The figure on plate 28 does not show clearly the flatness of 

 the tops of the whorls or the nodes on the margins of the flat places. Only one specimen 

 has been collected. 



Occurrence— -Mineola of Ralls County. 



Pleurotomaria isaacsi Hall and Whitfield 



P;ate 28, figures 1, 10, 11 



1873. Pleurotomaria Isaacsi Hall and Whitfield, New York State Cab. Nat. Hist. 

 23d Ann. Rept., p. 238, pi. 12, figs. 6 and 7. 



Hall and Whitfield's description — "Shell depressed, suborbicular, with moderately 

 elevated spire and rapidly increasing volutions, three to four in number, flattened or 

 slightly convex on the upper surface, rounded below, obliquely truncate on the periphery. 

 Umbilicus very broad and open. Surface of shell apparently destitute of ornamentation. 



This species bears much resemblance to the P. arata Hall, from the Schoharie 

 grit of New York and may be considered as a western representative species appearing 

 to hold a very similar geologic position. It differs in the absence of the transverse fur- 

 rows, crossing the upper side of the volutions, which characterize P. arata Hall." 



Remarks — This is a common form in the Snyder Creek shale, but most of the 

 specimens are misshapen, and the shape of the shell is the only means of identification. 



