PTEROPODA. 853 
SECTION B.—GyYMNOSOMATA, Bl. 
Animal naked, without mantle or shell; head distinct; fins 
attached to the sides of the neck; gill indistinct. 
Famity IT].—Crimwz. 
Body fusiform ; head with tentacles often supporting suckers ; 
foot small, but distinct, consisting of a central and posterior 
lobe ; heart opistho-branchiate; excretory orifices distant, on the 
right side; lingual teeth (in Clio) 12.1.12, central wide, denti- 
culated, uncini strongly hooked and recurved. 
Cxio (L.),* Muller. 
Litymology, Clio, a sea-nymph. 
Synonym, Clione, Pallas. 
Type, C. borealis, Pl. XIV., Fig. 45. (C. caudata, L., part.) 
Head with 2 eye tubercles and 2 simple tentacula; mouth 
with lateral lobes, each supporting 3 conical retractile processes, 
furnished with numerous microscopic suckers; fins ovate; foot 
lobed. In swimming, the Clio brings the ends of its fins almost 
in cortact, first above and then below. (Scoresby.) 
Distribution, 4 species, Arctic and Antarctic Seas, Norway, 
India. 
Sub-genus ? Cliodita (fusiformis), Quoy and Gaimard. Head 
supported on a narrow neck; tentacles indistinct. 4 species. 
Cape, Amboyna. 
PNEUMODERMON, Cuvier. 
Etymology, Pneumon, lung (or gill), derma, skin. 
Type, P. violaceum, Pl. XIV., Fig. 47. 
Body fusiform ; head furnished with ocular tentacles; lingual 
teeth 4.0.4; mouth covered by a large hood supporting two 
small, simple, and two large acetabuliferous tentacles, suckers 
numerous, pedicillate, neck rather contracted; fins rounded ; 
‘foot oyal, with a pointed posterior lobe; excretory orifice 
situated near the posterior extremity of the body, which has 
small branchial processes, and a minute rudimentary shell 
* This name was employed by Linneus for all the Pteropoda then known; his 
definition is most suited to the “northern clio,” probably the only species with which 
he was personally acquainted. The first species enumerated in the Syst. Nat. is 
C. caudata, and reference is made to an indeterminable figure in Brown’s Jamaica, 
and to Marten’s account of the Spitzbergen mollusc (C. borealis). In cases like this 
the rule is to adopt the practice of the next succeeding naturalist who defines the 
limits of the group more exactly. 
