260 Systematic Paleontology — Middle Devonian 



umbo to the margin and are crossed by concentric somewhat elevated 

 lamellae which are most conspicuous on the wing; on the right valve the 

 rays occur on the wing and the posterior half of the body of the shell 

 while the concentric lamellae are similar to those of the opposite valve. 



This specimen, in general, is quite similar to certain forms of A. 

 boydi except that the body of the left valve is strongly gibbous so that 

 there is a much greater difference in the convexity of the two valves, while 

 on the right valve the raj's extend over about one-half of its body instead 

 of being obsolete. It is thought that the marked difference in these two 

 characters is of sufficient importance to warrant the separation of this 

 specimen as a variety from the normal form of A. hoydi. This opinion 

 in the main is supported by that of Dr. Grabau who examined the speci- 

 men and stated that he would make it a new variety at least, emphasizing 

 the difference in .convexity of valves and the extension of rays on body 

 of right valve. 



Length, about 38 nrm. ; height, about 34 mm. 



Occurrence. — Eomney Formation, Hamilton Member. On Town 

 Creek 4 miles northeast of Oldtown; Town Creek Road at Geo. Diefen- 

 baugh's. 



Collection. — Mar}'land Geological Survey. 



ACTINOPTERIA SP. 



Plate XXX, Fig. 11 



Description. — Shell small and convex, the convexity of the left valve 

 being the greater which is quite marked on its body; ear small and sep- 

 arated by a shallow sulcus from the body, wing not sharply separated from 

 the body and outline unknown. The surface of the left valve shows 

 numerous simple, fairly strong rays, with generally a finer one between 

 two that are heavy ; crossed by regular, sharp concentric lines which give 

 a somewhat reticulated appearance to the surface. Eight valve exfoliated, 

 not showing the surface markings. 



This specimen is related to A. hoydi and is probably a new species but 

 on account of its broken and imperfect condition it is thought better not 



