Maryland Geological Survky 519 



Comparing the two forms, the following points of agreements and dif- 

 ferences may be found. The carapace in both is about equal in size and in 

 general outline. In each species the characteristic knobs or tubercles are 

 two in number, are situated in the dorsal region of the carapace and divide 

 the valves into three more or less equal portions ; the posterior tubercle in 

 U. conradi, however, is somewhat larger than its associate, while both 

 tubercles are of equal size in U. ceqimlis. Both species have a distinctly 

 raised marginal rim, equally developed in the genotype, but in the new 

 species under discussion, thickened and most prominent at the anterior 

 and posterior ends. A further distinction is afforded in the different sur- 

 face markings of the two species. The carapaces of both are reticulated, 

 but in U. cequalis the reticulation is so faint and loose meshed as to be 

 perceived only with difficulty, thus contrasting with the more closely 

 woven, regular reticulation of U. conradi. 



A European species, U. morgam (Jones), is also closely related but 

 differs from both in wanting the marginal rim. 



Length .86 mm. ; height .53 mm. 



Occurrence. — Oriskany Formation, Siiriver Member. 21st Bridge. 



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



Genus STREPULA Jones and Holl 



Strepula irregularis Jones and Holl 



Plate XCV, Figs. 12-15 



Strepula irregularis Jones and Holl, 1886, Ann. and Mag. Nat. Hist. (5), vol. 

 xvii, p. 404, pi. xiii, figs. 5, 7, 8, 9, 15. 



Description. — On the slabs and in the washings from the Keyser lime- 

 stone at Cumberland, are a number of specimens of an ostracod which 

 seem indistinguishable from the British Wenlock species described and 

 figured by Jones and Holl as Strepula irregularis. As suggested by its 

 specific name and shown in the figures on pi. xcv, the species varies con- 

 siderably in shape and in the distribution of their surface crests. The 

 variations of these features in the American form are no greater and in- 

 deed may be duplicated in the figures published by Jones and Holl, so 



