Wetter — Kinderhook Faunal Studies. 67 



cardinal extremities rounded. Pedicle valve depressed convex 

 near the beak, flattened on the sides, with a broad, shallow, 

 mesial sinus beginning in the middle of the shell and becom- 

 ing more conspicuous towards the anterior margin ; cardinal 

 area of moderate size. Brachial valve somewhat regularly 

 convex or gibbous. Surface marked by fine, closely arranged 

 radiating striae, and by a few indistinct lines of growth. In 

 the internal casts the muscular impressions are well defined. 

 Length 30 mm., breadth 38 mm., convexity of brachial valve 

 13 mm. 



Remarks. For a discussion of the relationship between the 

 later Devonian and the earlier Carboniferous species of the 

 genus ISchizophoria, the reader is referred to the first of these 

 Kinderhook Faunal Studies.* The Chonopectus sandstone 

 specimens do not materially differ from the Northview speci- 

 mens, and are more Carboniferous in aspect than Devonian. 

 The small specimen illustrated (Plate I. fig. 13) is the type of 

 Winch ell's species Orlhis flava, and is only an immature 

 example of iSchizophoria sivallovi. 



Chonetes illinoisensis Worthen. 



PI. If. 14. 



Shell of medium size, varying in outline from subelliptical 

 to semielliptical; the hinge line usually a little shorter than 

 the greatest width of the shell, and the cardinal extremities 

 slightly rounded. Pedicle valve rather strongly convex in the 

 middle, flattened towards the cardinal extremities ; the cardinal 

 margin furnished with five or six oblique spines on each side of 

 the beak. Brachial valve slightly concave, the concavity much 

 less than the con vexing of the opposite valve. Surface of 

 both valves marked with from 120 to 200 fine, rounded, 

 dichotomizing striae. The dimensions of an average specimen 

 are: length 10 mm. and breadth 13 mm. 



Remarks. The type specimens of Chonetes multicosta Win., 

 should be in the University of Michigan collection, but they 

 cannot now be found. The species is said to range all through 

 the Kinderhook and into the base of the Burlington limestone 

 at Burlington, Iowa. It most nearly resembles G . illinoisensis, 



* Trans. St. Louie Acad. Sci. 9: 13. 



