146 Systematic Paleontology — Middle Devonian 



Oldtown; Williams Eoad, 31/. miles southeast of Cumberland; B. & 0. 

 E. R. cut at 21st Bridge. 



Collection. — Maryland Geological Survey. 



Family PRODUCTIDAE 



Genus CHONETES Fischer de Waldheim 



Chonetes mucronatus Hall 

 Plate XI, Figs. 11-17 



Strophomena mucronata Hall, 1843, Geol. N. Y., pt. iv, p. 180, fig. 3. 

 Chonetes laticosta Hall, 1857, Tenth Rep. N. Y. State Cab. Nat. Hist., p. 119. 

 Chonetes mucronata Hall, 1867, Pal. N. Y., vol. iv, p. 124, pi. xx, figs, lorld; 



pi. 21, figs, la-lg. 

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



figs. 6, 7. 

 Chonetes mucronatus Schuchert, 1897, Bull. U. S. Geol. Surv., No. 87, p. 176. 

 Chonetes mucronatus Clarke, 1903, N. Y. State Mus., Bull. 65, p. 211. 

 Chonetes mucronatus Grabau and Shlmer, 1907, N. Am. Index Fossils, vol. ii, 



p. 235, fig. 286. 



Description. — Shell small, semioval to semielliptical ; moderately con- 

 vex (often flattened in shale and gibbous in limestone and arenaceous 

 deposits) ; hinge-line equalling or a little greater than the width of the 

 shell below, the extremities sometimes salient. The ventral valve is 

 often quite gibbous, regularly rounded in the middle, suddenly depressed 

 towards the cardinal angles which are flattened, and the area narrow and 

 linear. The dorsal valve is moderately concave to nearly flat, and the 

 area is scarcely more than the thickness of the shell. Surface marked 

 by from twelve to twenty usually coarse, rather distant, simple rounded 

 or subangular striae, a few of which on some specimens bifurcate to- 

 wards the margin. The cardinal margin marked by two or three spines 

 on each side of the apex, which are bent abruptly downwards and di- 

 rected outwards almost parallel to the hinge-line, so that the outer one 

 frequently appears to be a continuation of the cardinal extremity. In 

 the interior of the ventral valve is a strong median septum reaching 

 more than half the length of the valve, while the interiors of the valves 

 are strongly pustulose. 



I 



