108 SYSTEMATIC PALEONTOLOGY 



iferous. The punctge in the five or six centrally situated surface strise 

 are very fine, and the test unusually fragile. 



Length about 0.87 mm., height of left valve about 0.48 mm. 



Occurrence. — Calvert Formation. Plum Point. 



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



Cythere nitidula var. calvertensis n. var. 

 Plate XXXVI, Figs. 24-25. 



Description. — This variety or closely related species differs from the 

 typical form of C. nitidula in being a little more elongate and in the 

 coarser pattern of the surface punctation. The test also is stronger 

 and the anterior border narrower. While the three rows of surface punc- 

 ture, on the left valve, occur in a flattened area defined below by a faint 

 ridge. The outline approaches more nearly to that of C. porcella but is 

 still clearly distinguished by the greater prominence of the dorsal third 

 of the posterior curve. 



The right valve represented by Plate XXXVI, fig. 25, is believed to 

 belong to a variety of C. nitidula rather than to C. porcella, principally 

 because of the slight arcuation of the ventral outline. The correspond- 

 ing portion of the outline of right valves of C. porcella is always a trifle 

 sinuate. 



Length 0.8 mm., height 0.42 mm. 



Occurrence. — Calvert Formation. Plum Point. 



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



Cythere punctistriata n. sp. 

 Plate XXXVIII, Figs. 22-24. 

 Description. — Carapace compressed convex, subrhomboidal in outline ; 

 anterior margin obliquely subtruncate, narrowly rounded l^elow ; posterior 

 end, in the left valve especially, somewhat acuminate, sinuate above, 

 convex and curving rapidly forward beneath the extremity; dorsal and 

 ventral margins subparallel, the former gently convex, the latter very 

 slightly sinuate. Posterior 'end with a wide, flattened border, anterior 

 and ventral sides with a narrow one. Surface of valves having the 

 greatest convexity just behind and a little beneath the center, the 



