ISA CONTRIBUTIOX TO THE LoWER DEVONIAN FaUNAS OF MARYLAND 



Description. — " Shell obliquely ovate ; the left valve gently convex in 

 the middle, and becoming gibbous towards the beak, which in the young 

 shell is narrow and projecting above the hinge-line; right valve flat or 

 gently concave in the middle and below, and becoming slightly convex on 

 the umbo; anterior side gently curving to the base which is broadly 

 rounded, the curvature of the posterior side being more abrupt : anterior 

 wing small, trigonal, obtuse at its extremity, strongly defined from the 

 body of the shell : posterior wing three times as long as the anterior wing, 

 obtusely or subacutely pointed, extending more or less beyond the margin 

 of the shell, concave on the outer or lateral margin, its ju]iction with the 

 body of the shell not strongly defined. 



" Surface of the left valve marked by slender, sharply defined, rounded 

 radii, the principal of which are distant from two to four or five times their 

 width, and the spaces occupied by one, two or three finer interstitial radi- 

 ating stride (these radii are but faintly, and sometimes not at all per- 

 ceptible on the posterior wing, except along its upper margin, while they 

 are not seen on the anterior wing) ; concentrically marked by fine lamellose 

 strife, which, in the more perfectly preserved surfaces, are elevated and sub- 

 imbricating : these strias are usually conspicuous on both the anterior and 

 posterior wings. Surface of the right valve marked by broader and 

 scarcely elevated radii and less defined concentric strise." Hall, 1859. 



This species is rare in the Lower Devonian of Maryland. That it is 

 subject to wide variations is apparent from Hall's figures, and it may 

 be questioned whether that author has figured but one species. However, 

 no further light can be obtained from the few Maryland forms. 



Occurrence.— H'ELBETiBERG Formation, Keyser Member. Cumber- 

 land, Tonoloway ? CoEYiEAxs Me.a[ber. Dawson, Corriganvillc. Xew 

 Scotland Member. Dawson, Devil's Backbone. Horizon unknown. 

 Miller's Spring, Cedar Cliff, West A^irginia. Oriskany Formation. 

 Locality not known. 



Collections. — Maryland Geological Survey, U. S. iSTational Museum. 



Actinopteria communis (Hall) var. 



Description. — A few imperfect specimens from the Oriskany resemble 

 in a general Avay A. communis (Hall). The left valve shows fine, alter- 



