110 SYSTEMATIC PALEONTOLOGY 



the ventral edge until it becomes obsolete near the anteroventral angle, 

 attaining its greatest altitude in front of the midlength of the valve. 

 The furrows separating the first and second and the second and third 

 ridges are each occupied by a row of large pits, each pit of the second 

 row being divided into two compartments. The middle third of the 

 space between the third and fourth ridges contains three or four strong 

 cross bars, the depressed spaces between these being taken up by small 

 pits. The anterior third is divided longitudinally by a small ridge 

 separating a row of large pits above from a row of smaller ones beneath. 

 Between the posterior half of the ventral ridge and the ventral edge the 

 steep slope is occupied by four pits decreasing in size posteriorly, while 

 in front of these the slope carries several rows of much smaller pits. 

 Between the ventral ridge and the postcardinal border there is a large 

 depressed space. 



Length of a right valve 0.81 mm., greatest height of same 0.39 mm., 

 greatest thickness of same 0.29 mm. 



Although related to our C. piinctistriaia, the differences between their 

 respective surface markings are so striking that they cannot be con- 

 fused. A closer ally perhaps is found in C. truncata (Eeuss), a Tertiary 

 fossil of Austria and France, but C. vaughani is more elongate and 

 more acuminate posteriorly and differs also quite obviously in its sur- 

 face markings. 



Named for Mr. T. Wayland Vaughan, of the TJ. S. Geological Survey 

 in appreciation of the excellent work he is doing on the Tertiary corals. 



Occurrence. — Chesapeake Gkoup. James Eiver, Va. Probably also 

 in Maryland. 



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



Cythere fraxcisca n. sp. 



Plate XXXVIII, Figs. 19-21. 



Description. — ^Valves moderately and rather uniformly convex, acumi- 

 nate-ovate in outline, the posterior extremity small, subacute, com- 

 pressed, the anterior end broad, with a slightly oblique margin, curving 

 most in the lower half, the upper portion turning very gradually into 

 the dorsal outline; posterocardinal angle very obtuse; ventral outline 



