Characters of the genus Truncatella. 299 



The truncature of its columella excludes also from this genus Marji- 

 nella Auricula of Menard de la Groye, {Marg. buccinea, Risso, Hist. Nat. 

 IV. p. 232, and also identical according to F^russac with the fossil 

 Atiricula ringens of Lamarck,) see Fdruss. Tab], Syst. de la Fam. des 

 Auricules, p. 109. 



Class. Gasteropoda. 

 Order. Pectinibranchia. 



Fam. PALUDINIDiE. 



Genus Truncatella, Risso ; Cyclostomatos species, Drup. et 

 Lamarck; Paludinse species, Payraud; Turbo, Mont., Turt., &c. 



Tentacula (2 contractilia) cylindrico-conica, brevia, obtusa, basi 

 distincta, proboscide separata ; oculis sessilibus paullo supra basis angulum 

 externum positis. 



Caput proboscidiforrae exsertum. Os ad extremitatem proboscidis 

 cylindricse, inter tentacula exsertse, disciformera, supra emarginatam, 

 (sc. bilobam, ob buccas labiales in proboscidem ipsam coadunatas vel 

 commutatas.) 



Pallium collare siphone nullo ; orificio ad dextrum corporis, ut in 

 Helice, Melampode, Pedipede, &c. 



Pes rotundatus vel ovalis, brevis, minimus, posticus. 



Operculum corneum simplex, i, e. non spirale, ovale, apeiluram testae 

 omnino claudens.. 



Testa turrita ; adulta cylindrica, decollata vel truncato-obtusa : anfrac- 

 tibus distinctis, vel laevibus vel transverse costatis. Apertura ovalis, 

 brevis ; peritreraate continuo. Labrum simplex. Epidermis nulla. 



Animal littorale, amphibium, sed revera marinum et branchiis spirans. 

 Ingredienti, discus terminal is proboscidis pro pedis parte antica servit: 

 itaque modo ferfe larvarum Phalsenidarum Georaetrarum gradibus alternis 

 incedit. Testa junior, tereti-acuminata, e plunbus anfractibus quam 

 adulta constat: prioribus in plerisque demim (ut in Hel. BulinodecollatoJ 

 defractis, truncata evadit. 



It is now nearly three years since the acquisition of a single live 

 specimen of Cyclosioma truncatuhim, Drap.,and a long and continued 

 observation of its animal, convinced me that it was entitled to rank as a 

 distinct genus from any which were then constituted. I had accordingly 



