248 APORRHAIDiE. 



borealis must replace carinata in the present case ; and 

 it has_, besides^ the advantage of being in general use. 

 It is the Fusus umbilicatus of Smith, F. Las key i of 

 Macgillivray, Trichotropis costellatus of Couthouy, T. 

 acuminata of myself, T. atlantica (Beck) of MoUer, and 

 T. cancellata of Hinds. 



T. iyisignis of Middendorff occurs in the post-glacial 

 deposit at Bridlington, and was noticed by S carles 

 Wood as a variety of T. borealis. It inhabits Behring^s 

 Straits. 



Admete or Cancellaria viyndula (Tritonium viridulum 

 of Fabricius) is also extinct in these seas, its shell being 

 not uncommon in the Bridlington bed, as well as in the 

 Red and Coralline Crag at Sutton. It sundves in more 

 northern latitudes, and on the east coast of North 

 America. J. Sowerby described and figured this shell 

 as Murex costellifer ; it is the Admete crispa of Moller, 

 and has other names as a species of Cancellaria. Tros- 

 chel regards A. viridula as distinct from A. crispa, and 

 the genus Admete as the type of a family distinct from 

 that of Cancellaria. 



Family XXIV. APORRHA'IDiE, Troschel. 



Body spiral : mantle large and loose, forming a very short 

 branchial fold at the partially channelled base of the shell, 

 which it lines : snout cyhndrical, contractile, notched in front : 

 tentacles awl-shaped, separate : eyes on bulgings or short stalks, 

 at the outer base of the tentacles : foot small, lanceolate : gills 

 arranged in a single narrow plume : odontophore enveloped in 

 a sheath, straight ; rhachis single ; pleura? or uncini 3, plain- 

 edged. 



Shell, when young, spindle-shaped, never umbilicate : spire 

 turreted and tapering: mouth widely expanding: operculum 



