62 DENTALIUM-HETEROSCHISMA. 



tinued to both ends ; color whitish ; margin at the posterior end bul- 

 bous ; slit long and narrow, placed on the lower or ventral side ; its 

 length is double that of the greatest diameter of the shell. Length 

 0-6, breadth 0'075 inch. (Jeffreys). 



Davis Strait, 1785 fms. ; Off West coast of Ireland, 1180-1476 fms. 

 (Porcupine Exped.) ; off Azores Is., 1000 fms., Palma, Canaries 1125 

 fms., and off Pernambuco, Brazil, 675 fms. (Challenger). 



D. subterfissum JEFFR., Ann. and Mag. N. H. (4), xix, p. 154 

 (Feb., 1877) ; Proc. Zool. Soc. Lond., 1882, p. 660, pi. 49, f. 3. 

 WATSON, Challenger Scaphopoda and Gastrop., p. 10, pi. 1, f. 10 

 (1885). 



Peculiar in having the slit on the concave side of the tube. 



D. CALLITHRIX Dall. PI. 7, fig. 3. 



Shell white, moderately curved, laterally slightly compressed; 

 sculpture of about nine primary longitudinal ridges, angulating the 

 section, with between them toward the middle of the shell three to five 

 secondary smaller rounded threads, crossed by moderately strong 

 lines of growth ; the primaries are strongest posteriorly, they become 

 fainter in front and all the longitudinal sculpture nearly uniform 

 near the aperture in the adult ; aperture oblique, rounded oval, the 

 lower lip in advance, margin thin ; anal orifice circular, simple in 

 the young, without notches or slits ; adults usually show a short 

 broadish slit on the concave side, or are irregularly eroded; the 

 extreme tip in the young is more curved than the body of the shell, 

 and quite acute. Length 25 ; height of arch above chord, 5 ; ver- 

 tical diameter of aperture, 375 ; transverse ditto, 2'75 ; diameter of 

 anal end in young, 0*25 ; in figured specimen (eroded) 1 mill. The 

 shell may attain a length of 43 mill. (Dall). 



Yucatan Strait, 640 fms. ; Gulf of Mexico, Blake Station 20, in 

 220 fms. ; Station 41, in 860 fms.; near Guadelupe, in 769 fms., 

 sand, off Santa Lucia, in 423 fms., ooze, off Bequia, in 1591 fms., 

 ooze-, off Cape Fear, in 161 fms., ooze ; off Grenada] Also at U. S. 

 Fish Commission Station 2678, in 731 fms., ooze, off Cape Fear, North 

 Carolina, and in the Gulf of Mexico, between the delta of the Mississ- 

 ippi and Cedar Keys, Florida, in 1181 fms., mud ; S. of St. Kitts, 687 

 fms. ; East from Tobago, 880 fins. (Albatross) ; Rio Janeiro (U. S. 

 Expl. Exped.). 



D. callithrix DALL, Blake Rep., Bull. M. C. Z., xviii, p. 427, pi. 

 27, f. 10 (1889); Bull. U. S. Nat. Mus., no. 37, p. 76, pi. 27, f. 10 ; 

 Proc. U. S. Nat. Mus., xii, 1889, p. 294 (1890). 



