TERTIARY MOLLUSCA. 143 



identified by Dr. Dall as A. lyonii, is distinct from the Anguillan species, 

 having on the nepionic shell distinct flattened ribs with shallow, chan- 

 neled interspaces crossed by concentric, evenly spaced, not crowded, 

 elevated lines. If this is the true A. lyonii, the Anguillan fossil must 

 receive a different name. 



Localities. Crocus Bay, Anguilla, stations 6893, 6966, 6967, 

 Vaughan; Anguilla, Guppy; Sapote, Costa Rica, Gabb. 



Geologic horizon. Oligocene. 



Type. Philadelphia Academy. 



Figured specimens. U. S. Nat. Mus. No. 167136. 



Pecten (Amusium) antiguensis Brown. 

 (Plate 13, Figures 6, 7.) 



Pecten (Amusium) antiguensis Brown, Proc. Acad. Nat. Sci. Phila., p. 613, plate 18, figs. 1, 2, 

 3, 5, 1913. 



The following is the original description of this species: 



" Inequivalve, shell orbicular, rather thin, convex; the surface covered with 

 a fine concentric sculpture, following the growth-lines; with about 13 radial 

 ribs running from the beaks, where they are very pronounced, and, in one 

 valve, apparently disappearing towards the margin, but in the other valve 

 continued as undulations of the shell to the margin. The interior of the shell 

 has radial ribs extending to the margin, where the adjacent pairs of ribs con- 

 tract and are then seen to be paired, but otherwise seeming to be equally 

 spread as in P. (Amusium) lyonii Gabb, from which this species differs in 

 having a strong concentric sculpture (wanting in P. lyonii), and also in the 

 external radial ribbing being continued for a greater distance from the beak 

 than in Gabb's species. The species is also related to P. sol B. and P., but this 

 latter has shorter radial external ribs and the internal ribs are paired. The 

 ears are separated from the rest of the valve by a depression, as in the case of 

 P. sol. Length and height about equal 70-75 mm. 



"Hodge's Bay and Wetherill's Bay in the Antigua limestone, with Orbitoides, 

 etc., Oligocene." 



The Vaughan collection contains several well-preserved fragments of 

 this species. 



Locality. Station 6862, lower bed at Hodge's Bluff, Antigua, 

 Vaughan. 



Geologic horizon. Oligocene. 



Types. Philadelphia Academy, No. 1648. 



Figured specimen. U. S. Nat. Mus. No. 167139. 



Pecten (Hinnites) aratus, new species. 

 (Plate 12, Figures 2 a, b, 3, 4, 5, 6, 7.) 



The following is a description of this species: 



Shell large, convex, equilateral, flabelliform or suborbicular, inequivalve; 

 ribs 38, close-set, rounded, in mature specimens flattened distally, crossed by 

 fine, concentric, imbricate lamellae with spinose projections on the sides of the 

 ribs; interior narrowly channeled in harmony with the external ribbing; mar- 



