132 TBUNCATELLID-a:. 



to Pyramis ; Philippi and Michaud to Rissoa ; Fleming to 

 Turritella. 



The following species must be excluded from the genus : — 



Truncatella obesa, ilfen&e= Chondropoma. 



solida, J/en&e=Cyclostomus? 



terebralis, Menke (Turbo striatums, Linn.)= . . . ? 



littorina, Phil. "\ 



atomus, Phil. > = Paludinella. 



fusca, Phil. J 



ventricosa, Soto. = Tomichia, Bens. 



lineata, Held. ~\ 



lubrica, Held. > =Acicula. 



spectabilis, Held. J 



(??) dubiosa, C. B. Adams = Paludinella ? 



Quoyi, Pfr. (Cyclostoma striatum, Quoy and Gaim.) = 



Acicida ? 



Draparnaud was the first who described the animal of his 

 Cyclostoma truncatulum ; he said it was found on the ground 

 under plants, often buried in sand ; but in a note he proposes the 

 question, if it might not be rather considered as a marine mol- 

 lusk. Risso and Menke only regarded the characters of the 

 shell when they assigned to the genus its systematic place. 

 Lowe obsei"ved the form and habits of the animal, and was 

 induced to declare it a marine and pectinibranchiate mollusk, 

 although he noticed that it lived several weeks without water. 

 Michaud declares it to be terrestrial, living in moist spots on 

 sea-plants, but never submersed in water. Several authors fol- 

 lowed Lowe, others adopted the opinion of Michaud. Dr. L. 

 Pfeift'er collected living Truncatellce in places distant from the 

 sea, near Trieste and at Cuba, and recently the observations of 

 Poey and Guudlach have confirmed the terrestrial habits of 

 these animals ; he therefore considers that the genus must be 

 excluded from the Pectinibranchiata, and ascribed to the order 

 Phaneropneumona. There has been a doubt whether the eyes 

 are placed on the outer or inner side of the base of the tentacles. 

 Draparnaud says that the eyes are situated " above the posterior 

 base ;" De Cristofori and Jan, " on the posterior base ;" Lowe, " a 

 little above the outer angle of the base ;" Cantraine, " on the 

 inner base ;" Philippi, u on the superior base." These discre- 

 pancies of opinion have their origin in the extreme difficulty of 

 observing the organs of these minute animals ; but by the most 

 recent and accurate observations it seems to be proved that the 

 eyes are placed similarly to those of the genera Acicida and Geo- 



