104 SYSTEMATIC PALEONTOLOGY 



the ventral half is as in the latter. It difiEers from both in having the 

 surface punctse arranged in longitudinal lines between more or less 

 well developed ridges, in the greater width and more uniform curve 

 of the posterior end of the valves, this difference being more particu- 

 larly apparent when right valves are compared; and in the greater 

 development of the cardinal teeth and thinner connecting bar in the 

 right valve. Compared further with C. incequivalvis it will be found 

 that the carapace is higher, the ventral outline distinctly arcuate, in- 

 stead of straight or sinuate, the ends of the left valve broader, the 

 projection of the posterior extremity of the left valve beyond the 

 posterior hinge tooth less, and the excision of the outline just behind 

 this tooth also less. Finally, there is no sign of the broad subcentral 

 longitudinal furrows characterizing that species. Continuing the com- 

 parison with C. pleheia and its varieties, we find that the dorsal outline 

 of the right valve is much straighter and longer, and its ventral outline 

 either faintly arcuate or straight in the middle but never sinuate, while 

 the posterior end of this valve, as has been stated already, is wider and 

 more obtuse. The posterior end of the left valve also is more obtuse 

 and more uniformly curved, and usually is paralleled by a flattened 

 border, while the postdorsal angle is more prominent and the whole 

 dorsal outline straighter. 



As in the cases of the preceding species, we have failed to find any 

 exact match for C. hurns-i among described Tertiary and recent species. 

 A good many species of Cythere have been described and the fossil 

 species, as a rule, are widely distributed in Europe, but so far as our 

 investigations of American Tertiary Ostracoda permit of coming to 

 a conclusion on the point it appears that the number of new forms is 

 far from being exhausted and the species are nearly always distinguish- 

 able from their European congeners. 



Length about 1.15 mm., height 0.57 mm., thickness about 0.54 mm. 



The specific name is given in honor of the veteran collector, Mr. 

 Frank Burns, of the U. S. Geological Survey, who collected the material 

 from which many of the Ostracoda described in this volume were 

 picked. 



Occurrence. — Choptank Formation. Pawpaw Point. Calvert For- 

 mation. Plum Point. Chesapeake Group. Yorktown, Va. 



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



