49 



numerous close growth striae, also visible on the ribs. Apex with a wide deep slit totally cutting 



away the convex side of the apex over a varying distance of 0,5 to 1,5 mill. 



Margin on the convex side thin-edged on the concave side thick-edged. Anterior 



aperture keeled on the inner and narrowly arched on the outer margin, not oblique. 



a. Length 21, ^ mill., diameter of apert. 2,^ X 1,6 mill. 



6. Length 19 mill., diameter of apert. 2,2 X lo mill. Anterior aperture 



T 1 -n T r -11 o{ D. tricarinattim, 



c. Length 15 mul., diameter 01 apert. 2,2 X 1,5 mill. 



First is given the antero-posterior, then the lateral diameter, measured between the 

 lateral keels. 



Remarks. This form brings a second species into the subgenus BatJioxiphns. The only 

 hitherto known species of that subgenus, D. ensiculus Jeffreys is distributed over the eastern 

 and western Atlantic, Gulf of Mexico and the West-Indies. Both species are nearly allied, but 

 tricarinatiiin is shorter and more curved, has two prominent lateral keels and the slit is less 

 long than in cnsiciilus. 



Subgenus Gadilina Forest! 1895. 



1895. Gadilina Foresti, Bull, della Soc. Mai. Italiana XIX, p. 259. 



1897. Gadilina Foresti. Sacco, I MoUaschi del Piemonte e della Liguria, Parte XXII, p. 113. 



1897. Gadilina Foresti. PiLSBRY & Sharp, Man. of Conch., vol. XVII, p. xxxii. 



Shell smooth and slender, triangular or faintly triangular in section ; the concave side 

 flattened, the convex side rounded. Type D. triquetruvi Brocchi. 



This group was ranked as a subgenus of Siphonodentalmm^ but examination of the living 

 animal brought to light that it belongs to the Dentalidae, the foot having the regular epodial 

 sheath of species belonging to that family. 



KeytoSpecies. 



L Shell decidedly trigonal. 



a. The angles strongly accentuated stapes. 



a' . The angles more rounded insolitum. 



II. Shell cylindrical or faintly trigonal. 



a. Shell very slender and attenuated pachypleuriim. 



a . Apex strongly truncated trnncatuni. 



58. Dcntalium msolilnin E. A. Smith. PI. V, fig. 15. PL VI, figs 80, 82, 84. 



1894. Dentalium insolitum E. A. Smith, Ann. Mag. Nat. Hist. (6) XIV, p. 168, pi. 4, fig. 17, ija. 

 1897. Dentalium insclitum E. A. Smith. PiLSBRY & Sharp, Man. of Conch., vol. XVII, p. 109, 

 pi. 22, figs 56, 57. 



Stat. 45. 7°24'S., 1 18° 15'. 2 E. Flores Sea. 794 Metres. Fine grey mud, with some Radiolariae 



and diatomes. i Spec. 

 Stat. 52. 9°3'.4S., ii9°56'.7E. Sumba Sea. 959 Metres. Globigerina ooze. 3 Spec. 



SIBOGA-EXPEDITIE LIV. -j 



