78 DENTALIUM-FISSIDENTALIUM. 



top. Length 2'1 inch, breadth at mouth O22, at apex 0'036 inch. 



The young specimen from off Azores has at the apex on the con- 

 vex curve a slit 0*1 inch long, but interrupted by two bridges of the 

 shell which have not been removed when the fissure was made (pi. 

 8, fig. 34). 



From off the Azores the specimens belong to the typical form ; 

 that from Setubal, a remarkably large and fine specimen, belongs 

 to a variety : 



D. CAPILLOSUM var. PAUCICOSTATUM Wats., with only about 40 

 instead of 65 longitudinal riblets or threads, which are very flat on 

 their top and are divided by furrows remarkably broad and square 

 in form. These differences strike one very strongly at first, but the 

 transverse sculpture is identical, and there are spots on the typical 

 specimens which present an exactly similar form of ribbing. Figs. 

 35. (Watson). 



14 All the Blake specimens were dead or fragmentary, and most of 

 them belong to the variety paucicostatum Watson. In examining 

 the specimens named D. capillosum in the Jeffreys collection, I find 

 several of them which he regarded as the young to be of a more 

 slender and much smaller species, which probably never attains a 

 large size, though sculptured like D. capillosum. The specimen fig- 

 ured in the P. Z. S. above cited, is only about one-third the size of 

 an. adult." (Dalt). 



D. MAGNIFICUM E. A. Smith. 



An Indian Ocean species resembling D. capillosum, but with 

 decidedly coarser striation and longer slit. Aperture circular. 

 Length 101,diam. 13'4, length of slit 6*5 mill. It is known to us from 

 a specimen in the U. S. National Museum. So far as we can learn, 

 no description has yet been published. 



D. EXUBERANS Locard. 



Shell of relatively large size, very strongly conoid contour, very 

 wide at the base, tapering rapidly at first, then more progressively 

 to the summit ; profile at first straight, but quite conic for a short 

 distance from the base, becoming more curved further up, but 

 always quite moderately arcuate. Aperture very oblique, a little 

 undulated, visibly oval, contracted toward the dorsal, widened to- 

 ward the inner curve. Summit quite slender, rapidly tapering ; 

 apical slit elongated, ordinarily constituted of a series of narrow and 

 successive orifices, more or less regular. Shell quite thin but solid, 



