OF SANTO DOMINGO. 



211 



MANGDLIA. Leach, , • ■ 



M. hep tag on a. Gabb, la. s. 



Shell elongate, spire elevated, about three-fourths as lonj; as the mouth ; whorls eight, nuclear. Body whorl 

 rounded above the middle, sloping up to the suture and tapering nearly straight in^advance. Surface marked i)y 

 seven angular ribs with shallowly concave interspaces ; the whole crossed by minute, impressed lines. Mouth linear, 

 canal straight, outer lip thick, straight, acute on the margin ; sinus very small. Length .6 inch, width .25 inch. 



The largest of the four species, and easily recognized by its seven prominent ribs. 



M. polygon a. Gabb, n. s. 



Shell a little smaller, but nearly of the same shape as the preceding, slightly more slender ; surface marked by 

 about seventeen slightly sinuous, longitudinal ribs, with shallow, concave interspaces, crossed by numerous small 

 closely placed, revolving ribs. Aperture narrow ; sinus sinall with a small internal tubercle in advance. 



Distinguished from M. heiitagona by the numerous ribs and by the revolving 

 sculpture. ,^ , , , 



M. el e vat a. Gabb, n. s. 



Shell minute, sub- fusiform ; spire elevated, a little longer than the mouth ; whorls seven, flattened on the sides; 

 sub-truncated above ; body whorl tapering sinuously in advance. Surface marked by about nine or ten large longi- 

 tudinal ribs with deeply concave interspaces and crossed by finC) thread-like revolving, elevated striae. Aperture largCj 

 canal broad ; sinus deep, rounded, obliquely placed. Length .25 inch, width .1 inch. 



Recognizable by its size, not half as long as the two preceding; by its nearly equal 

 spire and mouth, and by the heavy longitudinal ribs. 



M. e 1 o n g a t a. Gabb, n. s. 



Shell small, very slender, spire twice as long as the mouth ; whorls eight, nearly flat on the sides ; body whorl 

 broadly convex, slightly narrowed in front. Suiface marked by six lai'ge longitudinal ribs with broad shallow inter- 

 spaces. Mouth narrow, canal short . sinus deep, narrow, oblique. 



Size about the same as that of M. elevata, but distinguished from it by the much 

 higher spire and the smaller number of ribs. 



All of these species, except M. polygona are very rare, and even that species can- 

 not be called common as compared with many of the other shells in the formation. 



TRITONIUM. Link. 



T. (Lampusia) lineatum. Brod. Proc. Zool. Soc. 1833, p. 6; not T. Uneatum, Sby. Proc. Zool. Soc. 1833, p. 72. 



The Santo Domingo fossils differ only from Galapagos specimens in that one of my 

 shells has larger varices than I find in the recent ones with which I compared it. The 

 two series agree exactly in sculpture, form, size and, in short, all of the details except 

 the individual difierence noted. 



T. (Cymatium) fe morale. Linn. sp. 



A few w^ell characterized specimens, the largest about five inches long. 



T. commutatum. Dk. 



My shell agrees perfectly in all its details with specimens of this species in the 

 Museum of the Academ3% marked from the West Indies. 



