TRUNCATELLID.E. 83 



of Deshayes : the fry was probably Adams's Turbo 

 strigatus. 



Turbo duplicatus of Linne, as well as his T. imbricatus 

 and T. exoletus (the last being T. ductus of Da Costa) 

 are tropical species of Turritella ; they were erroneously 

 introduced by Lister, Leach, Da Costa, and Montagu 

 into the list of British shells. 



Two arctic species of the present or an allied genus 

 occur in our glacial formation, viz. : — T.polaris of Beck = 

 T. erosa, Couthouy, at Bridlington (Woodward), and 

 Elie in Fife (Rev. Thomas Brown, fide Geikie) ; and T. 

 reticulata of Mighels and Adams = T. lactea, Mtiller, at 

 King Edward in Aberdeenshire ( Jamieson) . The former 

 of these has also been found in a fossil state by Mr. 

 Searles Wood in the Coralline Crag at Sutton, and by 

 Principal Dawson in Canada. 



Family XIV. TRUNCATE L'LID^, Gray. 



Body elongated : mantle plain-edged : head forming a cylin- 

 drical, contractile, and bilobed snout : tentacles conical, sepa- 

 rated by the snout : eyes sessile, or nearly so, placed a little 

 above (rather than outside) the bases of the tentacles : foot 

 short, and rounded at each end : gills consisting of a single 

 plume. 



Shell cylindrical : spire truncated on the animal arriving 

 at maturity, the opening thus made being filled up with a fresh 

 layer of shell : mouth oval, with a complete peristome : oper- 

 culum horny, ear-shaped, with a very short spire, having its 

 nucleus on the columellar or inner side of the mouth, near the 

 base of the shell. 



There is a great gulf between this family and the Tur- 

 ritellida?. Perhaps it is owing to a fault in the system 

 of classification — our motto being " nil deest nisi clavis '' 



