DENTALIUM-ANTALIS. 55 



being seen in the majority of adult specimens. D. semiclausum Nyst 

 has been referred here, but is probably distinct. 



D. CLAVUS Cooke. Unfigured. 



Shell solid, whitish, ungraceful, slightly arcuate, almost equally 

 wide from apex to base; fluted with about 11 very indistinct ribs, 

 interstices longitudinally lineated, the lines sometimes nearly equal 

 to the ribs ; apex entire. Length 1'75, diam. 0'2 inch. (Cooke). 



Gulf of Suez (Mac Andrew). 



D. clavus COOKE, Ann. Mag. Nat. Hist. (5), xvi, p. 275 (Oct., 

 1885). 



A remarkably ungraceful shell, reminding one of thick specimens 

 of novemcostatum Lam. The breadth is almost the same throughout, 

 ribs very indistinct and impossible to count at the base, interstitial 

 lines proportionately strong. (Cooke). 



D. SENEGALENSE Dautzenberg. PI. 13, figs. 13, 14, 15, 



Shell 35 mill, long, 5 wide at base ; rather thin, elongate, arcuate, 

 ornamented by 11-13 longitudinal narrow continuous ribs, narrower 

 than their intervals, and very delicate growth-striae between them, 

 the interstices without longitudinal sculpture. Apex entire. Aper- 

 ture polygonal, the peristome very acute, with 11 to 13 grooves 

 within corresponding to the external longitudinal ribs. Color uni- 

 form dull, milk white. (Dautz.*). 



Dakar, Senegal, ( l Melita ' Exped.). 



D. senegalense DAUTZ., Mem. de la Socie"te Zoologique de France 

 pour l'anne"e, 1891, iv, p. 53 (p. 38 of separate copy), pi. 3, f. 8a, 

 8b, 8c. 



D. senegalense approaches D. dentalis L. of the Mediterranean in 

 the equal ribs and white coloring; but it has only 11 to 13 longitu- 

 dinal ribs instead of 20, it enlarges more rapidly toward the ante- 

 rior end. It is less like the Mediterranean form described by us as 

 D. alternans (which name being in use for an earlier species described 

 by Chenu, we propose to replace by D. incequicostatum^), which has 

 alternately larger and smaller ribs. Finally, the shell approaches 

 D. lessoni Desh., reported by Lesson from New Guinea. (Dautz.*). 



GROUP OF D. DISPARILE. 



Irregularly many-ribbed species of rather small size, often with 

 alternating translucent and opaque encircling bands, or dots on the 

 ribs ; apex either simple, notched or tubiferous. 



