EEPORT ON THE SCAPHOPODA. 9 



cut off somewhat across the shell, supplies the anal orifice. L. 1'52 in., of young speci- 

 mens from Station 218 ; B. at mouth - 12, at apex 0'026. L. 1*14, of old and broken 

 specimen, Station 246 ; B. at mouth - 23, at apex - 14. 



Compared with Dentalium Icptoskeles, Wats., this is more curved, more conical, and thus not 

 nearly so attenuated. Compared with Dentalium agile, Sars, also, this is more curved, rather more 

 conical, and very much more delicate. It is likewise, when full-grown, apparently larger than 

 either. Than Dentalium lubricatum, G. B. Sow., this broadens more rapidly, is more brilliant, the 

 circular strias are stronger, the longitudinal are finer, closer, and sharper. It is also straighter than 

 that species. Than Dentalium pretiosum, Nuttall, this broadens faster and is much more brilliant. 

 Dentalium perlongum, Dall, lacks the faint longitudinal strias ; is much straighter, and is more 

 slender : thus if one chooses a point where the breadth in the two species is equal, then within 

 about an inch Dentalium perlongum, Dall, is not so much as two-thirds of the breadth of Dentalium 

 acutissimum. Contrary to Mr. Dall's statement, however, the two species agree in having the anal 

 fissure on the convex side. 



In reference to the form of the apex, it may be observed that the separation of the Dentalia by 

 the absence (Dentalium) or presence (Entalis) of the cleft process cannot be maintained. In 

 Dentalium abyssorum, Sars, there are some with a fissured process, some with a fissure without any 

 process, some with neither fissure nor process. There are cases in which the fissure is very regu- 

 larly formed, in others it looks as if it had been gnawed, in others it resembles a break ; sometimes 

 it is on the convex curve, as is the general case, sometimes on the concave, as in Dentalium 

 inversum, Desh., and in Dentalium subtcrfissum, Jeffr. ; sometimes it is irregularly lateral, as occa- 

 sionally in Dentalium agile, Sars. 



10. Dentalium longitrorsum, Reeve. 



Dentalium longitrorsum, Reeve, Conch. Syst. 



„ ,, Reeve, Conch Icon., vol. xviii. pi. ii. fig. 9. 



„ „ Sowerby, Thes. Conch., part 20, vol. iii. p. 98, sp. 10., pi. cexxv. (Generis 



iii.), fig. 59, 60. 



Station 189. September 11, 1874. Lat. 9° 36' S., long. 137° 50' E. West of Cape 

 York, S.W. of Papua. 25 fathoms. Green mud. 



Habitat. — (British Museum) Zanzibar and China. 



In Reeve's Conchologia Iconica this species is given as = Dentalium politum, Desh. 

 (iiec Linn.), and = Dentalium lamarckii, Chenu. 



11. Dentalium compressum, Watson (PL I. fig. 9). 



Dentalium compressum, Watson, Prelim. Report, pt. 2, Journ. Linn. Soc. Lond., vol. xiv., 1879, p. 516. 

 Dall, "Blake" Exped. Prelim. Report, Bull. Mus. Comp. Zool. Camb. Mass., 

 vol. ix. (1880), p. 38. 



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. 



(ZOOL. CHALL. EXP. — PART XLII. — 1885.) Tt 2 



