TERTIARY MOLLUSCA. 127 



Scapharca (Scapharca) anguillana, new species. 

 (Plate 5, Figures 10 a, b.) 



The following is a description of this species: 



Shell of moderate size, inequilateral, with elevated prosoccelous beaks 

 situated at the anterior third; right valve with 31 rounded ribs separated by 

 flat interspaces of equal width, the ribs on the anterior end set with erect 

 rounded, disk-like tubercles with longer axis parallel to the lines of growth and 

 separated by narrower spaces; on the remaining ribs the tubercles are replaced 

 by low nodes which become obsolete near the posterior end of the shell; left 

 valve unknown; cardinal area with a raised margin, high, with about 8 wavy 

 grooves; hinge-line short, with about 58 teeth, small and vertical mesially, 

 larger and oblique distally. 



Alt., 30 mm.; Ion., 32 mm.; diam. of right valve, 8 mm.; length of hinge, 

 22 mm. 



This species is very closely related to A. chiriquiensis Gabb from 

 Chiriquf, Panama, from which it can be distinguished by the smaller 

 size and much greater number of tubercles on the Anguillan species. 



Locality. — Crocus Bay, Anguilla, station 6964, Vaughan. 



Geologic horizon. — Oligocene. 



Type.— TJ. S. Nat. Mus. No. 167044. 



Scapharca willobiana, new species. 



(Plate 5, Figures 11 o, b.) 



{naze o, figures 11 a, o.) 

 The following is a description of this species: 



Shell of moderate size, elliptical, with low beaks situated at the anterior 

 third. Valves with about 35 ribs with fine, regular, concentric beading, 

 except on the posterior slope, where the ribs are almost smooth; near the 

 margin the ribs are flattened and some of them show an incipient channeling 

 which probably becomes more pronounced on larger shells. Hinge line long, 

 straight. Both ends of shell rounded, the anterior with shorter radius than the 

 posterior. Spaces between the ribs nearly equal in width to the ribs and 

 crossed by evenly spaced, raised lines continuous with the beads on the ribs. 

 Cardinal area long and narrow. 



Long., 23 mm.; alt., 15 mm.; diam., 9 mm. 



The type is a young specimen which has been crushed in the umbonal 

 region but is otherwise well preserved. 



This species may be distinguished from Scapharca hypomela Dall by 

 its much more elliptical outline, rounded margins, and fewer ribs. 



Locality. — North side of Willoughby Bay, Antigua, station 6881, 

 Vaughan. 



Geologic horizon. — Oligocene. 



Type.—U. S. Nat. Mus. No. 167040. 



Pinna vaughani, new species. 

 (Plate 9, Figures 4 a, 6.) 



The following is a description of this species : 



Shell rapidly expanding, valves mesially carinate; sculpture of longitudinal 

 riblets about 7 on dorsal area and about 5 below the carina, lower half of 

 ventral area smooth, except for growth lines. 



Length of fragment, 58 mm.; height, 37 mm.; depth, 28 mm. 



