Weller — Kinderhook Fanned Studies. 13 



MOLL.USCOIDEA. 



BRACHIOPODA. 



Orthothetes chemungensis (Conrad). 



Shell more or less semi-elliptical in outline, unsymmetrical, 

 the greatest width usually being along the hinge-line ; both 

 valves often distorted to a greater or less extent because of 

 the attachment of the living shell. Pedicle valve usually 

 moderately concave but sometimes nearly flat, elevated at the 

 beak and around the margin, beak often distorted. Brachial 

 valve convex, the greatest convexity usually at about the 

 center, somewhat compressed towards the cardinal extremi- 

 ties. Surface of both valves marked bv radiatino: costae 

 which usually increase by intercalation with some regularity, 

 and by more or less prominent lines of growth. Sometimes 

 the whole surface is covered by \cvy fine concentric ridges 

 which are most prominent between the radiating costae. 



Remarks. OrUioihetes chemungensis is one of the most 

 variable species of brachiopods known, the great variation in 

 form being due, perhaps, in part, to the attachment of the 

 shell during life to some extraneous object by the point of 

 the beak. A good idea of the oreat deofree of variation of 

 the shell may be had by examining Hall's* illustrations of the 

 species from the Chemung group of New York. There is 

 almost no character of the species which can be said to be 

 constant, except its great variability. Among the Northview 

 fossils there are numerous specimens, all in a more or less 

 fragmentary condition, which are identified with this species. 

 Some of them may be compared with 0. desideratus Hall 

 and Clarke, from the Waverly group of Ohio, but they con- 

 stantly differ from that species in the less convex brachial 

 valve, the less concave pedicle valve, and in the greater 

 relative length of the hinge-line. None of the specimens are 

 perfect enough to be worthy of illustration. 



SCHIZOPHORIA SWALLOVI (Hall). 



Fl. IV. f. 7. 



The genus Schizophoria is abundantly re[)resented in the 

 Devonian faunas west of the Mississippi River, and in the 



* Pal. N. Y. ♦. pi. 10. 



