GASTROPODA. 277 



much less prominent. Young specimens of 4 whorls show 3 very 

 distinct rounded keels on the last whorl, the lowest arising from the 

 suture. The protoconch is the same as in the species. Suture not 

 excavated, well impressed, the whorl forming a narrow flat or very 

 lightly concave band below it. Size the same as the species. 



Animal unknown. 



Type in the Mus. Hist. Nat., Paris. 



Hab. Auckland Harbour (H. S.) ; near Channel Island, Hauraki 

 Gulf, in 25 fathoms ; South Island (teste Hutton) ; Little Barrier 

 Island, in 20 fathoms (R. H. Shakespcar) ; Bay of Islands (J. C. 

 Anderson). 



Fossil in the Pliocene of Wanganui. 



Fossil adult specimens show the 3 keels on the last whorl much 

 more distinctly than I have seen it on Recent forms. 



Earn. XENOPHORID^E, Philippi. 

 Onustidce, H. and A. Adams. 



Animal with long, annulated muzzle ; elongated, subulate ten- 

 tacles, with sessile eyes at their external base ; foot small, used for 

 jumping, not walking, with the anterior portion expanded, posteriorly 

 tapering ; gill long, composed of narrow laminse and filaments. Den- 

 tition 2+ 1+ 1 + 1 + 2; the central tooth subtrigonal, multicuspid ; 

 laterals large, subtriangular, the margin reflected and multicuspid ; 

 the marginals very narrow and long, arcuated. 



Shell depressed or conical, trochiform, with carinated periphery, 

 not nacreous ; very often soldering shells, stones, &c., to its upper 

 surface. Operculum large, horny, subannular, with lateral dextral 

 nucleus, musciilar impression sinistral, semilunar. extending the 

 whole length. 



These molluscs scramble along like the Strombs ; they extend 

 and fix the front dilated part of the foot, and draw the posterior por- 

 tion up to it, jerking the shell forwards at every movement ; this 

 mode of progression is adapted to the nature of the surface on which 

 they move, which is usually composed of the debris of dead shells. 

 The peculiarity of this family is the habit of agglutinating foreign 

 bodies to the upper surface of the shell, which is carried to such an 

 extent in some instances as to conceal the volutions and give, the 

 structure the appearance of a small pile of fragments of stones and 

 shells. This imitation of its surroundings is no doubt protective 

 in its nature. Of the shells attached, single valves of Lamellibranchs 

 are preferred ; the interior of these is always turned up and free. 



The species Xenophora conchyliophora dates back to the Eocene 

 of North America, and is still living in the West Indies, which is a 

 strong testimony to the protective value of the device by which the 

 members of this family defend themselves. (Ball.) 



