Weller — Kinderhook FauncU Studies. 457 



The dimensions of a small specimen are : width of shell at 

 aperture 14 mm., extreme length of shell 12 mm., height of 

 shell from plane of aperture 7.5 mm. The dimensions of 

 one of the largest specimens are: width of aperture 17 mm., 

 length of shell 16.5 mm. 



Remarks. This species is quite distinct from any of the 

 Devonian or Mississippian species heretofore described, and 

 unlike so many species in the fauna, it seems to have no close 

 ally in the Hamilton faunas of New York. In form and pro- 

 portions it approaches B. hilahiatus W. & W., from the 

 Chonopectus fauna of the Kinderhook at Burlington, Iowa, 

 but the dorsal slit is very much shallower than in that species 

 and the elevated portion of the dorsal band is much shorter 

 and much less sharply carinate. The species occurs in abund- 

 ance in the Glen Park fauna, and exhibits considerable varia- 

 tion although the variation is for the most part in the adult 

 or very old shells and is largely restricted to the more abruptly 

 expanded portion of these shells near the aperture. 



The species is named in honor of Mr. E. O. Ulrich of the 

 U. S. Geological Survey, who first called the writer's atten- 

 tion to this interesting fauna. 



BeLLEROPHON JEFFERSONEN8IS U. »p. 



Plate 2, fig. 24. 



Description. Shell small, umbilicate, the outer volution 

 flattened on the dor«um, increasing regularly in size, moder- 

 ately expanded near the aperture. Aperture subelliptical in 

 outline, with a very shallow dorsal notch. Surface marked 

 with a flat or slightly depressed dorsal band which is crossed 

 by very fine lines of growth following the direction of the 

 dorsal slit; the sides of the shell marked by regular trrnsverse 

 costae much coarser than the lines of growth across the dorsal 

 band. 



The dimensions of a large specimen are : width of aperture 

 10 mm., length of shell 10.6 mm., height of shell above plane 

 of aperture 7 mm. 



Remarks. This is one of the rarer species in the Glen 

 Park fauna, and at first it was thought to be a variation of the 

 last species. The two species are evidently related, but B. 



