MARYLAND GEOLOGICAL SURVEY 109 



anterior and dorsal slopes appearing rather fiat. Surface ornament 

 consisting of single or double rows of minute puncta? situated in five 

 or six shallow grooves, having their best development in the posterior 

 half and so arranged that they converge toward the anteroventral angle. 

 Most of the grooves and punctas, however, become obsolete before reach- 

 ing that point. Marginal spines wanting. 



Length of a right valve 0.62 mm., greatest height of same 0.33 mm., 

 greatest thickness of same 0.15 mm. 



C. pimctistriata might be compared with a number of European spe- 

 cies, but we are at a loss to say to which of a dozen or more it is most 

 allied. Under the circumstances it may suffice to express our conviction 

 that it is specifically distinct from all previously described species of 

 which we have seen either specimens or good figures. The next species, 

 C. vaughani is probably a nearer ally than any other known to us. 



Occurrence.— C-aoTTAy-K Formation. Peach Blossom Creek, 3 miles 

 southwest of Easton. Calvert Formation. Church Hill. 



Collections.— JJ. S. :N"ational Museum, Maryland Geological Survey. 



Cythere vaughani n. sp. 

 Plate XXXVIII, Figs. 25-27. 

 Description. — Valves subacuminately produced posteriorly, oblique 

 anteriorly, this end being rounded below and subtruncate above, also 

 much wider than the other; dorsal outline wavy on account of the 

 surface ornament, convex on the whole, with the cardinal angles fairly 

 distinct in the right valve; left valve not seen; dorsal half of posterior 

 edge sinuate, as is also the ventral outline; lower half of anterior rim 

 and posterior two-thirds of ventral edge with a fringe of minute spines. 

 Surface with four longitudinal ridges, of which the first forms the 

 anterior half of the dorsal outline; the second begins at the post- 

 cardinal angle and extends forward beneath the first to a point under 

 the anterocardinal angle where it is lost; the third begins a little 

 in front of the postcardinal angle, near which it is very prominent, and 

 extends quite across the valve to about the middle of the anterior rim; 

 the fourth likewise extends nearly the full length of the valve, begin- 

 ning at the posterior extremity and running parallel with and close to 



