168 Bulletin 29 333 



anterior ribs show a deep medial groove extending well up towards 

 the beaks, and on each side of this a shallower groove; the cen- 

 tral ribs just anterior to the umbonal ridge have several longi- 

 tudinal grooves; the ribs of the posterior slope beginning near 

 the angle of the umbonal ridge are flatter, nearly smooth, and 

 little sulcate. The ribs are wider than the interspaces and 

 crossed by concentric raised lines which produce a beaded appear- 

 ance especially near the center of the shell. Compared with 

 other West Indian species of the same group it is distinguished 

 by its oblong form, base nearly parallel to the hinge, and less 

 produced umbonal ridge. Length 50, altitude 29, thickness of 

 one valve 15 mm. 



Fide Dall, Guppy's A. consobrina from Jamaica is halido?iata 

 Dall, which is shorter and higher, with a more arcuate base. 



Localities. — (Exp'd '16) Bluff 2, Cercado de Mao; Zone B, 

 Rio Gurabo at Los Quemados. Valves probably young of this 

 species were found in Bluff 3, Cercado de Mao and on the Samba 

 Hills at approximately 540 feet altitude. 



Scapharca golfoyaquensis, n. sp. 



Plate 28, Figure 5 



This is another member of the group to which A. Henekeni 

 belongs. The ribs number thirty-eight and the ribbing is nearly 

 the same, but the central ribs appear to be narrower and less 

 divided. The central ribs of the left valve are conspicuously 

 beaded while those of the right valve are smoother, flatter and 

 more square, whether the latter character is true of Henekeni we 

 do not know as all our valves are left. The chief difference be- 

 tween A. Henekeni and. golfoyaquensis lies in the form, the latter 

 species being conspicuously and constantly much more produced 

 and pointed posteriorly, the beaks are fuller and more anterior. 

 Instead of being oblong the shell is broad posteriorly and narrow 

 anteriorly ; cardinal area long and moderately wide, with a few 

 concentric grooves; hinge line long with numerous vertical teeth 

 somewhat oblique at the posterior end of the series. Length 59, 

 altitude 3 1 , thickness of one valve 1 6 mm. 



