538 Systkmatic Paleontology 



octoxaria ix.equalis 11. sp. 

 Plate XCVIII, Figs. 12-18 



Description. — Valve ovoid to subrhomboidal ; left valve larger and over- 

 lapping the right on all sides; ornament of left valve consisting of two 

 parallel curved dopressions in the dorsal portion, the outer the less con- 

 spicuous, and of two or more smaller depressions with their corresponding 

 ridges just within the anterior half and a little beneath the crater of the 

 shell ; the right valve of the same carapace shows a similar arrangement of 

 the grooves in the dorsal half, but the anterior and ventral depressions are 

 in part unrecognizable or absent and so arranged that the general aspect 

 is very different from that of the opposite (left) side of the shell. 



Length of a complete carapace 0.7 mm. ; width 0.50 mm. ; thickness 

 0.3? mm. 



Occurrence. — Heldeubekg Formation, Keyser Member. Cumber- 

 land. 



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



Octonaria simplex (Krause) 

 Plate XCVIII, Fig. 1!) 



Thlipsura simplex Krause, 1891, Zeits. deutsch. geol. GeselL, vol. xliii, p. 508, 

 pi. xxxii, fig. 16. 



Description. — Among the numerous specimens of Ostracoda from the 

 Keyser limestone is the single presumbably right valve figured, which 

 agrees essentially with the figures of Octonaria simplex (Krause), 

 from the Silurian drift of northern Germany. The subcentral pit or 

 sulcus at first recalls Primitia, but the convex cardinal margin is indic- 

 ative of overlapping valves as in Octonaria and Thlipsura. More material 

 is necessary to determine the true genetic relations of this form, and until 

 this is forthcoming, it seems best to regard the species as above. 



Length of right valve 0.80 mm.; width 0.57 min. 



Occurrence. — Helderberg Formation, Keyser Member. Cumber- 

 land. 



Collection. — U. S. Xational ^Fuseum. 



