154 Dr. J. Gwyn Jeffreys on 



for a quarter of an inch : colour whitish : margin at the 

 posterior end having a short and narrow notch. L. 1-4. 

 B. 0-15. 



Station 12, 1450 fms. ; 13, 690 fms. ; 16, 1785 fms. 

 ' Porcupine ' Expedition, 1869, Bay of Biscay, 862 fms. ; 

 north of the Hebrides, 542 fms. : 1870, off the coast of Por- 

 tugal, 220-1095 fms. Off Bahia Honda, Gulf of Mexico, 

 418 fms. (Pourtales). *■ Challenger ' Expedition, off the 

 Azores, 450 and 1000 fms. 



This appears to attain a size considerably exceeding that 

 given in the above description, as fragments measure nearly 

 ■y^ inch in breadth. 



Dentalium ensiculus*, Jeffr. 



Shell tapering, considerably and regularly curved through- 

 out, compressed or flattened, thin, nearly transparent, and 

 glossy : sculpture, a sharp keel on both the dorsal and ven- 

 tral sides (giving the appearance of a double-edged scimi- 

 tar), besides occasionally a few slight and irregular longitudi- 

 nal keels or raised striae and concentric lines of growth : 

 colour clear-white : sUt of moderate length and very broad, 

 semicylindrical, placed on the upper or dorsal side ; the poste- 

 rior or narrower end of the shell is nearly bisected to form the 

 slit, the upper part being abruptly truncated ; when viewed 

 sideways the lower part appears split ; the point is rounded and 

 entire. L. 0-9. B. O'l. 



Station 12, 14-50 fms. ; 16, 1785 fms. : fragments are not 

 uncommon. ' Porcupine ' Expedition, 1869, off the west of 

 Ireland, 1366 fms. ; Bay of Biscay, 862 fms. : 1870, off the 

 coast of Portugal, 740-1095 fms. 



The annual or occasional growth is sometimes shown by 

 the irregular formation of the new or succeeding portion of 

 the shell, which is narrower than the former or preceding por- 

 tion. 



Dentalium subterfissum f, Jefir. 



Shell slender and finely tapering, more curved towards 

 the point, rather thin, nearly semitransparent, and glossy : 

 sculpture, from 12 to 16 delicate and sharp regular longitudi- 

 nal striae, which are continued to both ends : colour whitish : 

 margin at the posterior end bulbous : slit long and narrow, 

 placed on the lower or ventral side ; its length is double that 

 of the greatest diameter of the shell. L. 0*6. B. 0*075. 



* A little sword. t Slit underneath. 



