148 Systejiatic Paleoxtolooy — Middle Devoxiax 



CoUrrtions. — .Mai'vlaiid Oeologica! Survey; New York State Museum; 

 AuH'rican ]\rus(Hiin of Natural Ilistorv. 



Chonetes coronatus (Conrad) 

 Plate XI, Figs. 18-21 



Strophomena varinata Conrad, 1842, Jour. Acad. Nat. ScL, Phila., vol. viii, 



p. 257, pi. xlv, fig. 13. 

 Strophomena syrtalis Conrad, 1842, Jour. Acad. Nat. Sci., Phila., vol. viii, 



p. 253, pi. xiv, fig. 1. 

 Chonetes coronata Hall, 1857, Tenth Rep. N. Y. State Cab. Nat. Hist., p. 146, 



figs. 1, 2. 

 Chonetes coronata Hall, 1867, Pal. N. Y., vol. iv, p. 133, pi. xxi, figs. 9-12. 

 Chonetes coronata Keyes, 1891, Johns Hopkins Univ. Circ, vol. xi, p. 29. 

 Chonetes coronata Hall and Clarke, 1892, Pal. N. Y., vol. viii, pt. i, pi. xvi, 



figs. 10, 11, 24, 26, 33, 39, 41, 43. 

 Chonetes coronatus Schuchert, 1897, Bull. U. S. Geol. Surv., No. 87, p. 173. 

 Chonetes carinatus Clarke, 1903, N. Y. State Mus., Bull. 65, p. 209. 

 Chonetes coronatus Grabau and Shimer, 1907, N. Am. Index Fossils, vol. ii, p. 



236, fig. 288. 



Description. — Shell large, broadly elliptical, some of the single valves 

 approaching a rectangular form; the hinge-line is sometimes shorter 

 than the width of the shell and the cardinal angles rounded, but gener- 

 ally it is nearly or quite equal to the greatest width of the shell with the 

 lateral margins nearly rectangular to the hinge-line; the cardinal angles 

 are sometimes produced in short acute auriculate extensions. "\'entral 

 valve varying from moderately convex in the younger shells, to very 

 gibbous in the older ones; sometimes a little flattened below the umbo 

 and this space gradually widens toward the front, more frequently there 

 is a shallow undefined sinus along the middle of the valve; the outline 

 of the valve is regvdarly convex, but abruptly depressed towards the cardi- 

 nal extremities, which are flattened and a little deflected toward the ven- 

 tral side; the cardinal margin has from Ave to seven oblique spines on 

 each side of the apex, although they are usually not preserved on the 

 Maryland specimens, and the cardinal area is narrow. Dorsal valve is 

 variably concave, sometimes following nearly the contour of the ventral 

 valve, but often moderately concave or nearly flat in the middle and 

 upper part, and more suddeidy deflected towards the front and lateral 



