Maryland Geological Survey 537 



Genus OCTONARIA Jones 

 OCTONARIA ? ANGULATA 11. sp. 



Plate XCVIII, Figs. 9-11 



Description. — Valve semicircular, the anterior and dorsal sides regu- 

 larly curved, the ventral edge straight, the post-ventral angle clearly 

 defined and approximately rectangular, the antero-ventral region blunt 

 and somewhat obliquely truncated. Surface of valves depressed, convex, 

 with a thin rim-like marginal ridge; within the latter a similar ridge 

 essentially paralleling the outer one; finally a straight or curved thin 

 ridge divides the median space longitudinally into subequal parts. The 

 depressed spaces between the ridges show obscure, irregularly distributed 

 papillae. 



Length of an average left valve .75 mm. ; height .50 mm. 



Of this singular species, nothing but the separated valves have been 

 observed. Their reference to Octonaria is of course somewhat provisional, 

 none of the hitherto described species being at all close. It is possible also 

 that the hinge has been misinterpreted and that the straight edge may be 

 the cardinal instead of the ventral side. The very slight convexity of the 

 surface is somewhat foreign to the conception of Octonaria, as is also the 

 marginal ridge. The latter feature and also the inner ridge are somewhat 

 suggestive of Strepula, but after careful comparison, it was decided that 

 there was really no relationship to that genus. Considering the straight 

 edge as dorsal, another relationship which may be suggested is to certain 

 species of Kirkbya. However, pending further information respecting the 

 hingement and relation of the valves to each other, the above designation 

 will serve provisionally. 



Occurrence. — Helderberg Formation, Keyser Member. Cumber- 

 land, Maryland; Keyser, West Virginia. 



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



