10 THE VOYAGE OF H.M.S. CHALLENGER. 



Shell. — Compressed between its concave and convex curves to the extent of 0'016 in.; 

 bent, as in young shells, a little more towards the apex, and the curve greater on the 

 convex slope, slightly carinated on each side. Sculpture : Faint, but very regular ; longi- 

 tudinal striae, about O'Ol in. apart, apparently in the texture of the shell, which thus 

 seems to be built up of minute, square-faced rods laid side by side. Crossing these at 

 right angles are sharp, irregular scratches in the line of growth, nearly circular, but bent 

 a little forwards on the concave curve. L. 0'45 in. B. at mouth 0'05 (least), 0'06 

 (greatest) ; at apex O'Ol 9. 



In my Prelim. Report (loc. cit.) I said that it was very possible that this might be a Siphodentcdium, 

 as Mr Gwyn Jeffreys suggested ; but that in the absence of the animal and the rubbed condition of both 

 ends of the shell, it was impossible to say. Mr Dall (loc. cit.) seems to have been able from his material 

 to settle this point, for he speaks positively on the matter, and says it is not a Siphodentcdium. It 

 resembles Siphodentcdium tctragonum, Brocchi, more than any other ; but the want of the angles, the 

 different character of the longitudinal strias, and, above all, the compression, separate it completely. 

 There is only one dead, discoloured, and somewhat rubbed specimen. 



12. Dentalium subterjissxim, Jeffreys (PI. I. fig. 10). 



Dentalium subterfissum, Jeffreys, "Valorous" MolL, Ann. and Mag. Nat. Hist. ser. 4, vol. xix., 



1877, p. 154. 

 „ „ Jeffreys, "Lightning" and "Porcupine" Moll, Proc. ZooL Soc. Lond., 



1882, p. 660, pi. xlix. fig. 3. 



Station 78. July 10, 1873. Lat. 37° 26' N., long. 25° 13' W. Azores. 1000 

 fathoms. Volcanic mud. 



Station 85. July 19, 1873. Lat. 28° 42' N., long. 18° 6' W. Palma, Canaries. 

 1125 fathoms. Volcanic mud. 



Station 120. September 9, 1873. Lat. 8° 37' S., long. 34° 28' W. Pernambuco, 

 South America. 675 fathoms. Eed mud. 



Habitat. — Davis Strait. 17 85 fathoms. North Atlantic; various Stations off the 

 West Coast of Ireland. 1180 to 1476 fathoms (Jeffr.) 



This species, like Dentalium inversum, Desh., is peculiar, as having the apical slit on the concave 

 curve. The animal is unknown. 



13. Dentalium didymum, 1 Watson (PI. I. fig. 11). 



Dentalium didymum, Watson, Prelim. Report, pt. 2, Journ. Linn. Soc. Lond., vol. xiv. 1879, p. 517. 



Station 24. March 25, 1873. Lat, 18° 38' 30" N., long. 65° 5' 30" W. N. of 

 Culebra Island, West Indies. 390 fathoms. Pteropod ooze. 



1 di'dvfio;, as two-sided. Also from St Thomas ; also as doubtful. 



