186 



Bulletin 39 



358 



Area Henekeni Maury Plate 24, figs 13, 14 



Area consobrina Sowerby, 1849, Quart. Journ. GeoL Soc. London, voL 



6, p. 52, pL 10, fig. 12. Not of d'Orbigny, 1844. 

 Area consobrina Guppy, 1876, Quart. Journ. GeoL Soc. London, voL 



32, p. 531. 



Area eonsobrina Dall, 1888, Trans. Wagner Free Inst, Sci., voL 3, pt. 

 4, p. 646. 



Area eonsobrina Sheldon, 1916, Paleont. Amer., No. i, p. 49. 

 Area Henekeni Maury, i9i7,BulL Amer. Pal., vol. 5, p. 331, pi. 29, fig. 2. 

 Area {Scapharea) sobrina Pilsbry and Johnson, 1917, Proc, Acad. Nat. 

 Sci. PhiL, vol. 64, p. 186. 



Our shells from Water Cay are similiar in form and general 

 sculpture to the A. Henekeni Maury {^A. consobrina Sowerb}^), 

 from the Miocene of Santo Domingo, the only noticeable differ- 

 ence being the greater number of ribs on the Panama shell. The 

 ribs of Henekeni from Water Cay average about 39 in number, 

 and 35 to 36 on the Dominican shells. The ribs of the left 

 valve are evenly beaded or granulated by concentric threads 

 which pass across the interspaces as elevated threads. The 

 ribs of the posterior-dorsal submargins are nearly smooth. 

 They are more or less divided at the anterior extremity and 

 very finely beaded. 



Length 29, height 18.25, diameter 14.15 mm. 



31, 18, semidiameter of right value 



7.25 mm. 



Gatiin Stage: Water Cay. 



Area costaricensis, n. sp. Plate 25, figures i, 2 



Shell moderately large, elongate, convex, with the beaks sit- 

 uated at the anterior i-3;ventral margin but gently curved to the 

 attenuated and pointed posterior extremity; right valve with 

 about 30 ribs, of which the most anterior and posterior ones are 

 rather wide, the others narrow; interspaces on the center or the 

 disk 3 times or more the width of the ribs; the ribs of the right 

 valve are obscurely granulated on the anterior extremity, more 

 or less smooth on the center but on the posterior extrem- 

 ity, they are double and peculiarly granulated along their sides; 



