﻿26 NORWOOD AND PRATTEN ON CHONETES. 



C. Flemingii, nob. — PL II., fig. 5, a, b, c, d, e. 



Shell rather small ; depressed ; transverse, having its greatest breadth on the car- 

 dinal border. Dorsal valve covered with a great number of slender, filiform ribs, 

 which frequently bifurcate and amount, when they reach the free borders of the shell, 

 to about 150. It is provided with a tolerably deep and wide sinus. The area is 

 formed at the expense of both valves. Deltoid aperture rather wide. Ears some- 

 what flattened, and separated from the dorsal vault by a very decided depression. 

 Cardinal edge ornamented by seven tubes on each side of the beak, which are directed 

 obliquely. In the furrows between the ribs are numerous shallow depressions, as 

 represented in the magnified view of a portion of the shell, PI. II., fig. 6, e. The 

 ventral valve is furnished with a varix, corresponding to the sinus of the opposite 

 one. Its ribs are like those of the other valve, but become obliterated on the ears. 



Internal 'part of the dorsal valve. — There is a strong ridge projecting from the 

 beak towards the middle of the shell ; on each side of which there is a large and 

 deep depression. Most of the remaining surface is covered with large granulations, 

 which, however, stop short of the free margin of the shell. Around this may be 

 seen a series of ribs corresponding to the furrows between the exterior ribs, and 

 showing a series of fine granulations, which answer to the small depressions of the 

 exterior. 



Dimensions. — Length, 10 millimetres ; breadth, 17. 



Geological Position and Locality. — It is found in beds of shale, ten miles North 

 West of Richmond, Missouri. The age of the beds has not yet been determined. 



Explanation of the Figures. — PL II., fig. 5, a. View of the dorsal valve. 



Fig. 5, b. — View of the ventral valve and area of the same specimen. 



Fig. 5, c. Longitudinal section of the same. 



Fig. 5, d. Interior of the dorsal valve. 



Fig. 5, e. Magnified view of a portion of the shell. 



C. Verneuiliajsta, nob. — PL II., fig. 6, a, b, c. 



This is one of the most singular species of the genus. It is small, transverse, 

 having its greatest breadth on the cardinal border. Its beak is much larger and 

 higher than that of any of our other Chonetes. An extremely deep sinus extends 

 from the beak, bordered on each side by a high ridge ; outside of which there is 

 another sinus separating the ridges from the ears, which are a little rounded and 

 much extended. Its surface is covered with about 100 ribs, very fine and dichoto- 

 mous. Area tolerably large, and formed at the expense of both valves. Deltoid 

 aperture very wide. Cardinal edge with four tubes on each ear, directed obliquely. 

 The ventral valve is furnished with a very decided varix, corresponding to the sinus 

 of the opposite valve. Its ribs are like those of the dorsal valve. 



Dimensions. — Length, 7 millimetres; breadth, 12. 



