GASTEROPODA. 119 



is no evidence whatever of such striae. I do not, however, at present find 

 any sufficient reason for separating them from those figured on plate 24, in 

 which the posterior part of the last volution is distinctly tricarinate. 



Bellerophon M^ra. 



PLATE XXV, FIGS. 9-H ; and PLATE XXVI, FIGS. 19-24. 



Bellerophon Mccra, Hall. Illustrations of Devonian Fossils: Gasteropoda, pi 22. 1876. 



" Neleus, H.& W. Illustrations of Devonian Fossils: Gasteropoda, pi. 22. 1876. 



Not " " " Geol. Rep. U. 8. Survey, 40th Parallel : Clarbncb King, Geologist (in MS.). 



Shell subglobose, or broadly subovoid; length about equal to the greatest 

 width at the aperture ; in imperfect specimens the width is usually greater 

 than the length. Inner volutions small and gradually enlarging to the 

 third, which is more rapidly expanded, the exposed portion of the outer 

 one being extremely ventricose. Aperture greatly expanded, the peris- 

 tome broadly sinuate in front and auriculate at the sides; somewhat 

 thickened and repand as it approaches the umbilicus, over which it 

 extends, continuing in a thickened callosity across the columellar side. 



The dorsum is marked by a distinct carina and the entire surface by strong 

 pustulose striae, or rows of pustules, which are arranged along lines parallel 

 to the stria? of growth. The dorsal carina is also pustulose. These markings 

 are somewhat less conspicuous on the anterior and lateral margins of the 

 shell. 



This fossil, when entire, presents a strong rotund form until near the aper- 

 ture, where it becomes abruptly expanded. The shell is thick, and the surface 

 completely studded with rows of pustules which, in one direction, are arranged 

 in series parallel to the lines of growth in the shell, and, in the other direction, 

 in diagonal lines crossing these, giving the aspect of a quincunx arrangement. 

 On the removal of the shell the carina on the cast usually extends but a short 

 distance from the margin of the aperture, and the dorsum beyond this is 

 obtusely or obscurely angular. In a few examples, which present no marks of 

 specific distinction, the carinate dorsum is continuous for the entire extent of the 



