116 SYSTEMATIC PALEOXTOLOGY 



ARTHROPODA. 



Class CRUSTACEA. 



Superorder MALACOSTRACA. 



Order DECAPODA. 

 Family CANCROIDEA. 



Description. — Claws belonging to an indeterminate genus of the 

 Gancroidea are abundant in the bed underlying the indurated ledge at 

 Up|)er Marlboro. 



All of the specimens are so fragmentary that no attempt is made to 

 illustrate the forms. 



Collection. — Maryland Geological Survey. 



Superorder OSTRACODA. 

 Family BAIRDIIDAE. 



Genus BYTHOCYPRIS Brady. 



Bythocypeis subaequata n. sp. 

 Plate XVI, Figs. 1-4. 



Description.- — Carapace about 1.0 mm. in length, elongate, subcylin- 

 drical or, perhaps better, subreniform, the dorsal outline arcuate, the 

 ventral slightly hollowed, and the ends rounded and nearly equal, the 

 posterior a trifle blunter than the anterior; end view nearly circular, 

 dorsal and ventral views lanceolate, with the greatest thickness about 

 the middle of the posterior half; left valve slightly overlapping the 

 right along its ventral edge; surface smooth or very finely granulose. 

 Inner side of valves with simple thin edges, and within these, except 

 along the dorsal border, a thin bevelled plate, much the widest an- 

 teriorly. 



There are numerous fossil and recent Ostracoda, mostly of otherwise 

 widely diverging genera, that have a carapace similar to this, but none 

 was found exactly niatchiu"- it. 



