GASTEROPODA. 191 



CLASS— PTEROPODA. 



Ord. THECOSOMATA. 



Cleodora.* Peron. and Lessueur. 1810. 

 Clio (spec.) Linn. 

 Hyalea (spec.) Lam. 

 Vaginella. Daudin. 

 Cliodora. Schweig. 

 Creseis et Cuvieria. Rang. 1828. 

 Balantium. Children, (fide Gray.) 

 Crisia. Menke. 1844. 



Gen. Char. Shell thin, fragile, and transparent ; inversely pyramidal, posterior 

 extremity closed and acuminated ; anterior open, dilated in the centre, with lateral 

 compressed aliform appendages. 



In the recent state these shells are of a hyaline and vitreous texture, extremely 

 thin and fragile, clear and crystalline as the thinnest and most transparent glass. 

 That beautiful character has disappeared in the fossil, and they can scarcely be 

 recognised in their altered condition. 



The known animals belonging to this genus are all marine, and frequenters of 

 deep and open seas, where they swim by means of wing-like fleshy fins, and appear 

 like aquatic butterflies. The same power of locomotion is possessed by some of the 

 Bullae, which, in some of the characters of the animals, they much resemble. Species 

 of this genus are found fossil in the Sicilian beds. 



1. Cleodora inpundibulum. S. Wood. Tab. XXI, fig. 14, a — b. 



Cleodora infundibulum. S. Wood. Catalogue, vol. ix, p. 459, pi. 5, fig. 13, 1842. 



CI. Testa subulato-conicd, laevigata, infundibuliformi ; antice apertd, dilatatd ; postice 

 elongatd, acuta, extremitate compressd, utrinque carinatd. 



Shell elongate, tapering, trumpet-shaped, smooth, and fragile ; posterior part 

 elongated, and acuminated, with a compressed extremity ; anterior open, dilated, 



* Etym. Cleodora, a proper name. An. vero Cliodor a ? Hermansen. 



