( 56 ) 



CLASS II. PTEROPODA 



GENERA. 



A. Head distinct. 



1. Clio. Lin. 



No mouth ; head form- Fins with a vasculary 



ed by two rounded lobes ; net-work instead of 



tentacula small. PI. 15, branchisc. 

 fig. 3. 



2. Cleodora. Per on. 



Two membranous 

 wings with the mouth 

 between, having a small 

 lip. 



3. Cymbulia. Peron. 



A large fin with three 

 lobes, two tubercles and 

 a small fleshy beard at 

 the base of the smallest. 



No shell. 



An envelope. PL 5. 

 fig. 2. 



Envelope cartilagi- 

 nous or gelatinous. PL 

 5, fig. 3. 



4. LlMACINA. (1) CUV. 



Head and wings resem- 

 bling those of the Clio : 

 body terminated by a spi- 

 ral tail lodged in a very 

 thin shell. 



A shell. 



5. Pneumodermon. Cuv. 



Branchise on the sur- No mantle. No shell, 



face of the body ; fins 

 small ; a Small lobe or 

 fleshy tentaculum beneath 

 the mouth. PL 15, fig. 

 4, 5. 



B. Head indistinct. 



6. Hyalea. Lam. 



Two large wings ; man- A shell, 



tie cleft at the sides, bran- 

 chiae within the clefts. 

 PL 14, fig. 8. 



(1) This animal also uses its shell as a boat,, and its wings as oars, when it swims 

 on the surface of the sea. The species known (Clio Helicina of Phipps. Gmel. Ar- 

 gonauta arctica, Fabric Faun. Grcenl. 387 ) is scarcely less abundant in the northern 

 seas than the Clio borealis, and, like it, is said to be one of the principal aliments of 

 the whale. 



