CLASS Il. PTEROPODA. 
GENERA. 
A. Head distinct. 
1. Guo. Lin. 
No mouth; head form- Fins with a yasculary _No shell. 
ed by two rounded lobes; net-work instead of 
tentacula small. Pl. 15, branchie. 
fig. on 
2. Creopora. Peron. 
Two membranous An envelope. PI. 5. 
wings, with the mouth fig. 2. 
between, haying a small ‘ 
lip. 
3. CymeButias. Peron. 
A large fin with three Envelope cartilagi- 
lobes, two tubercles and nous or gelatinous. PI. 
a small fleshy beard at 5; fie, 3: 
the base of the smallest. 
, 
4. Limacina. (1) Cuv. 
Head and wings resem- A shell. 
bling those of the Clio: 
body terminated by a spi- 
ral tail lodged in a very 
thin shell. 
5. PNEUMODERMON. Cuv. 
Branchie on the sur- No mantle. No shell. 
face of the body ; fins 
small; a small foe or 
fleshy tentaculum beneath 
hi ha PL 45, fig. 
48 
B. Head indistinct. 
6. Hyarea. Lam. 
Two large wings ; man- A shell. 
ue cleft at the sides, bran- 
chie 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. Grant. 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. 
