ENDycH.] ' DEVONIAN. 213 



A small Prodmlm was found, resembling P. suhaeuleatus ; occurs 

 sparingly. Orthoceras is found, but in a very poor state of preservation. 

 Athyris and Bhynchonella occur. Bellerophon and JEuomphalus were col- 

 lected in imperfect specimens. 



By far the most numerous and varied species occurring there is the 

 one described by Professor Meek as — 



Ehynchonella Endlicht, Meek. 



Shell attaining a rather large size, subtrigonal, with breadth nearly 

 or quite equaling the length, the widest part being in advance of the 

 middle, becoming very convex with age anteriorly ; posterior lateral 

 margins straight, or but slightly convex in outline, laterally compressed 

 or flattened, and diverging from the beaks, in adult specimens, usually 

 at about right angles or less; anterior lateral margins rounding to the 

 front, which is generally more or less produced, and, as seen in a direct 

 view from above or below, transversely truncated or a little sinuous at 

 the middle. Dorsal valve very convex, particularly along the middle, 

 the elevation increasing rapidly to the front, which js raised so as to 

 form a very prominent, broad, rounded, or somewhat flattened, and 

 slightly-defined mesial fold, rarely traceable back to the central region, 

 while, on each side, the lateral slopes descend abruptly to connect with 

 those of the other valve; beak moderately prominent, and incurved more 

 or less nearly at right angles to general j)iane of the valves ; interior 

 with a prominent mesial septum extending forward nearly half way to 

 the front. Ventral valve flattened at the umbo, and so broadly and pro- 

 foundly sinuous from near the same anteriorly as to leave only a promi- 

 nentangular margin on each side, the sinus being broadly flattened along 

 the middle, and increasing rapidly in depth to the front margin, which 

 is curved upward more or less nearly at right angles to the plane of the 

 valves, and produced in the middle, in the form of a large extension 

 fitting into a corresponding sinuosity in the middle of the front of the 

 other valve; anterior lateral margins on each side of the sinus meeting 

 those of the other valve at acute angles ; posterior lateral margins very 

 abruptly deflected and rectaugularly deflected along each side of the 

 sinus, to meet those of the other valve; beak comparatively small. 

 Surface of both valves ornamented by numerous radiating costse, which, 

 on the umbones, are merely distinct raised lines, but increase in size 

 anteriorly, particularly those in the sinus and on the mesial fold, where, 

 toward the front of adult specimens, they become moderate-sized, 

 rounded ribs, of which four to six or seven may be counted in the imme- 

 diate flattened bottom of the sinus, and two or three more on the fold, 

 while those on the lateral slopes bifurcate, and continue, of smaller size, 

 to the anterior and anterolateral margins. (Finer surface-markings 

 unknown). 



Length of an adult specimen, 1.78 inches ; breadth, 1.53 inches; con- 

 vexity, about 1.24 inches. 



This is a fine species, more nearly resembling some Devonian and 

 Upper Silurian forms than the usual Carboniferous types. Its most 

 marked features are the large size of its mesial sinus, the flattening of 

 its posterior lateral slopes, and the angularity of the posterior lateral 

 margins of its ventral valve on each side of the sinus, formed by the 

 abrupt flexure of those margins to meet those of the other valve. This 

 inflection of the posterior lateral margins gi\:es this part of the shell a 

 peculiar truncated, rectangular appearance, contrasting strongly with 

 the very acute angles formed by the connection of the autero-lateral 

 margins of the valve. 



