202 Bulletin 39 374 



more flattened left valve and lower, smaller ribs of its right. In 

 i7i<xqiialis, the fine, lamellose, concentric lines cover the entire 

 interspaces between the ribs on both valves, while in the present 

 species the interspaces of the left valve are largel}'' smooth with 

 the concentric lines confined to the extreme umbonal area. 

 Gatiin Stage: Coll. /, Red Clijf Creek. 



I mile soictk of the beach, along Old Man Sam 

 Creek. 



Coll. ^, East Grape Point Creek. 



Rio Blanco. 



Section AEQUiPECTEM, Fischer 



Pecten (Aeqiiipecten) preglyptus, n. sp. Plate 17, figures 2, 7 



Shell of moderate size, subcircular in form and convex; ears 

 of usual size, subequal and with a straight hinge-line; sculpture 

 of about 16 or 17 wide, little elevated ribs and narrower, scarce- 

 1}^ distinguishable interspaces; the surface is otherwise smooth 

 or with fine, concentric lines; interior of the shell with 29 or 30 

 Am.usiumA\k.& internal lirse which are evenly spaced and not in 

 pairs; these lir^ are very faint in the middle of the shell cavity 

 but strong- distally. 



Length 50, height 49, semi-diameter 6.5 mm. 



An Afnusium-Wke species found in the lower sandstones and 

 conglomerates of the Gatun formation in upper Codes Creek. 

 It is closely related to the recent deep-water Pecten glyptus Ver- 

 rill from the cost of Hatteras and Marthas Vineyard (see Dall 

 Proc. U. S. Nat. Mus., vol. 12, p. 248, pi. 8, figs. 2, 3), both 

 species having about the same number of low, wide ribs and in- 

 ternal lirse. The fossil shell seem to have been nearly circular 

 ^\\\\^ glyptus is decidely oblique in outline. 



Gatun Stage: Upper Codes Creek. 



