30 DENTALIUM. 



The group Coccodentalium is hardly equivalent in value to the 

 subgenera we have recognized, being merely a modification of the 

 D. agassizi type. 



D. CARDUUS Ball. PI. 7, fig. 6. 



Shell pure white, sometimes attaining an ashy or rusty tinge from 

 extraneous matter, elongated, slightly curved, and with a rasp-like 

 surface for about half its adult length ; longitudinal sculpture of 

 very numerous fine sharp raised threads with somewhat wider inter- 

 spaces, in which intercalary threads from time to time arise ; trans- 

 verse sculpture of fine sharp elevated lamellae which cross the threads 

 and become almost spinulose on the intersections ; these can be felt, 

 but are almost too fine to be clearly seen with the naked eye ; in 

 the perfectly adult shell, this sculpture becomes, through senility or 

 wear, less sharp on the last half of the shell ; though both sorts of 

 ridges persist, they are thicker and more rounded ; shell not very 

 thick ; aperture circular, very little oblique ; anal orifice small, with 

 a short wide slit on the convex side, and no notch or wave on the 

 other. Length of completely adult shell, 87*0 ; height of arch from 

 chord, 7'0; diameter of aperture, 7'0; of anal orifice 0*7 mill. 

 (Dolt). 



Near Santa Lucia, in 116 fms. ; in 154 fms., ooze, near Granada 

 (Blake). Also by U. 8. Fish Commission, in 338 fms., on the Little 

 Bahama Bank. 



D. carduus DALL, Blake Rep., Bull. M. C. Z., xviii, p. 423, pi. 

 27, f. 3 (1889) ; Bull. U. S. Nat. Mus., no. 37, p. 76, pi. 27, f. 3. 



The specimen figured is only 16 mill, long, but shows sufficiently 

 the characters of the form and sculpture. Better specimens were 

 afterwards found in some of the Fish Commission dredgmgs, from 

 which the above description is drawn. The peculiar sharpness felt 

 by drawing the shell gently between the finger and thumb is very 

 recognizable and under the glass the sculpture is very beautiful. 

 (Dall). 



A closely allied species attains a very large size in the Oligocene 

 of San Domingo. 

 D. CANCELLATUM Sowerby. PI. 10, fig. 67. 



Shell thin, white, acuminate, strongly curved towards the apex, 

 where it is cancellated by about 8 longitudinal ribs and elevated con- 

 centric strict, then the shell becoming straighter and the ribs more 

 numerous (Sowb.). Length 25 J, greatest diam. 3 mill, (from fig.). 



China (Sowb.). 



