256 



ox TlIP] TOPOGRAPHY AND GEOLOGY 



and ends rounded ; surface smooth or bearing a few faint impressed concentric lines on the anterior part near the 

 base. Length .85 inch, width .15 inch. 



PECTEK. Linn. 

 P. opercular is. Linn., sji. - 



Osireu, id. Linn. " , 



Pecten, id. Lam. Rve. Icon. up. 54. 



Some worn specimens, with the scnlpture eroded from the ribs, agree in all acces- 

 sible details with this common European species. 



This fossil is found, not only in the usual localities in the Cibao, but also occurs 

 near San Cristobal. 



p. in equal is. Sby., Quart. Jour., Vol. VII., p. 52. ^ 

 Id. Guppy, Quart. Jour., Vol. XXIL, p. 394, pi. 18. flg. 0. 

 Slightly inequivalve, ribs rounded. 



Common in the Cibao, and found by Mr. Bonaczy at Loma Cristina on the south 

 side of the Island, near San Cristobal, 



p. oxygonum. Sby., Quart. Jour. Geol. Soc, Vol. VI., p. 52. 

 P. exasperatm. Guppy, loc. cit. , Vol. XXIL, p. 294. 



This species may be, as Mr. Guppy thinks, a variety of exaspevatus, but it seems 

 to me rounder, with smaller ears, and with two or three more ribs, 



p. thetidis. Sby., Quart. Jour., A^ol. VII., p. 52. 



Two varieties of this shell occur, with the same form and number of ribs. The 

 first has the ribs square, with a longitudinal groove, or the angle of the rib is ex- 

 tended into a roughened ridge which stands erect. The other variety has the rib 

 also flat or grooved, but the angulai" ridge is well marked and stands out laterally. 



p. eccentric us. Gabb, n. s. * 



Shell slightly inequivalve, sub-circular, oblique, eai-s sm.all, surface covered with twenty-two fiat ribs, sometimes 

 slightly grooved, and with concave intersi^accs. Diameter 1 to 1.5 inch. 



ISTearest to P. irradiaiis, Lam., but more oblique, and with broader, flatter Jiibs. 



p. a ug u s t i c o s t a t u s. Gabb, n. s. 



Shell small, elongated sub-circular, equilateral ; ears small ; base and sides regularly curved ; surface marked 

 by about twenty-three x^rominent, very narrow and acute ribs. 



Of the size and general style of P. oxygonum, this shell is distinguished by its 

 peculiar ribs, which have a narrow, almost knife-like edge. 



P. i n t e r 1 i n e a t u s. Gabb, u. s. 



Shell slightly convex, nearly equilaterjfl, base and sides evenly rounded ; ears large, radiately ribbed '; surface 

 m9,rked by about eighteen round or sub-augulated ribs, with a single small line in each interspace. Length 1 inch. 



About the size of the preceding, this shell is longer and flatter, with a marked 

 difference in the character of the ribs. 



p. magnificus. Sby., Proc. Zool. Soc, 1835, p. 109. 



A single specimen was found b}^ Mr. Bonaczy. I cannot find any difference 

 between it and the Columbian ^hcll. - 



