336 TROCHIDJS. 



we should call stifling or suffocating. Another peculiar 

 habit of such mollusks is worthy of notice, and is one 

 which I cannot pretend to explain. It is the faculty of 

 floating. Now it is very certain that in their native 

 habitat, at a depth of from 150 to 540 feet, these shell- 

 fish, being ground-dwellers and having no organ or 

 means by which they can rise to the surface, could never 

 exercise this faculty. Is it instinct that teaches them to 

 float after having been forcibly dragged from the bottom 

 of the sea and put into a shallow vessel of water ? and if 

 so, when was it implanted? Two living specimens, 

 which I took in the same spot, differed in the colour of 

 the animal, although the shells were undistinguishable. 

 One was of a uniform yellowish-white, while the other 

 was milk-white and had the sides of the foot streaked 

 with brown. Mr. Alder says that the tongue is very 

 beautiful and of a complicated structure, and that the 

 uncini on each side are extremely numerous. It agrees 

 in general character with that of T. zizyphinus : indeed 

 the animals of both are much alike. The first whorl of 

 the fry is exquisitely reticulated, like Lagena squamosa. 

 The present species is the T. alabastrum of Beck (ac- 

 cording to Loven), T. quadricinctus of S. Wood, and 

 Ziziphinus alabastrites of Gray. No wonder that 

 Forbes, who described this shell as a new species, gave 

 it the name of formosus. It is truly beautiful ; and we 

 offer but faint praise in saying of such splendid prizes 

 of the dredger 



" There's not a gem, 



Wrought by man's hand to be compared to them." 



