no. 1823. MOLLUSKS OF THE GENUS CERITHIOPSIS— BARTSCH. 357 



CERITHIOPSIS BICOLOR, new species. 

 Plate 38, fig. 6. 



Shell small, elongate-conic, white, excepting the base of the posterior 

 row of tubercles which is light brown. (Nuclear whorls decollated.) 

 Post-nuclear whorls flat, marked by three spiral rows of tubercles, 

 of which one is at the summit of the whorls, another immediately 

 above the peripheral sulcus, and the third a little nearer the one at 

 the summit than its anterior neighbor. These tubercles are con- 

 nected by narrow bands into a spiral cord and axially by slender 

 riblets, the two inclosing well -impressed squarish pits. Of these 

 tubercles, 16 occur upon the first four of the remaining turns, 18 

 upon the fifth to seventh, and 20 upon the eighth and the penul- 

 timate turn. Suture strongly constricted. Periphery of the last 

 whorl marked by a slender spiral cord. Base smooth. Aperture 

 rhomboidal, decidedly channeled anteriorly; posterior angle obtuse; 

 outer lip rendered sinuous by the external sculpture, columella short, 

 strong and twisted. 



The type has lost the nucleus and several of the early post-nuclear 

 whorls; the ten remaining measure: Length 4 mm., diameter 1.2 

 mm. The type and three specimens (Cat. No. 195214, U.S.N.M.) 

 were dredged at U. S. Bureau of Fisheries station 2813 in 40 fathoms 

 on coral sand bottom, bottom temperature 81° off Galapagos Islands. 



CERITHIOPSIS ARNOLDI, new species. 

 Plate 39, fig. 3. 



Shell elongate-conic. (Nuclear whorls decollated.) The post- 

 nuclear whorls slightly rounded, ornamented by three tuberculate 

 spiral keels of which one is at the summit, the anterior at some little 

 distance above the suture, and the third halfway between the two. 

 The posterior of these three keels is much weaker than the other two 

 on the early turns, but gradually increases in size until on the last 

 volution it is practically equal to them. In addition to the spiral 

 keels, the whorls are marked by somewhat protractive axial ribs, 

 which are about as strong as the spiral keels and render them tuber- 

 culate at their junction. Of these ribs, 14 occur upon the first of 

 the remaining turns, 16 upon the third, 18 upon the fourth, 20 upon 

 the fifth, 22 upon the sixth, 24 upon the seventh and eighth, and 

 26 upon the penultimate turn. The spaces inclosed between the 

 ribs and spiral cords are strongly impressed rounded pits. Sutures 

 moderately constricted, showing the posterior edge of the first 

 basal cord. Periphery of the last whorl marked by a deep sulcus, 

 as wide as those occurring between the spiral cords on the spire 

 and, like them, crossed by the continuations of the axial ribs. Base 

 very short, almost flattened, somewhat concave near the columella, 



