New Species of Devonian Fossils. 123 



In the ventral valve the hinge-teeth are strong, supported by 

 dental plates which continue forward on the floor of the valve 

 as very slightly diverging ridges reaching to the center of the 

 valve and bounding the small, slender, deeply impressed muscle- 

 scars. The muscle-scar is deeply bilobed in front, each half 

 tapering out to a sharp point alongside the ridges just described. 

 In the dorsal valve the cardinal process is exceedingly minute, 

 the dental sockets well developed, the brachial lamellae strong 

 and produced forward as a distinct ridge bounding the narrow 

 elongate muscle-scars which reach the middle of the valve. 



Dimensions: The average specimen has a length of 9 mm.; 

 width, 10 mm.; depth, 4 mm. A large specimen: length, 12 

 mm. : width, 1 1 mm. ; depth, 6 mm. 



Discussion: This species resembles D. postelegantula of the 

 Decker Ferry of New Jersey, but in comparison with that species 

 it is smaller, more nearly circular in outline, less carinate on the 

 ventral valve, its dorsal sinus extends to the beak, and it is more 

 finely lined. Compared with D. concinna of the Keyser forma- 

 tion, this shell is much smaller, more finely lined, lacks the cari- 

 nation of the ventral valve, and has a relatively small cardinal 

 area. It is perhaps closest to D. elegantiila of the Niagaran, but 

 that species is proportionately longer and its dorsal valve is flat 

 or concave. 



Occurrence: Common in the Rockhouse shale at the sulphur 

 spring and at Rockhouse, both on Horse Creek, Hardin County. 



Dalmanella macra, n. sp. 

 Plate II, figs. 9, 10 

 Description: Shell transversely subelliptical in outline, hinge- 

 line a little shorter than the greatest width of the shell, cardinal 

 extremities sharply rounded. The ventral valve is subcarinate 

 along the median line, but the lateral slopes are gently concave, 

 giving the shell an emacerate appearance. The dorsal valve is 

 slightly convex in the umbonal region, but concave in the ante- 

 rior portion. The valve bears a median sinus which is narrow at 

 the beak but widens rapidly anteriorly and loses its distinctness 

 in the general concavity of the valve. Ventral muscle-scars 

 extremely small, almost embraced between the hinge-teeth. 



