322 



MOLLUSCA. 



by one whorl and a half, umbilicated on one side, and flattened on 

 the other. The animal uses its shell as a boat and its wings as pars, 

 whenever it wishes to navigate the surface of the deep. 



Clio helicina, Phips and Gmel.; Argonauta arctica, Fab., Faun. 

 Groenl., 387. Almost as common on the arctic seas as the 

 Clio borealis, and is considered as forming the chief source of 

 food for the Whale(l). 



Hyalea^ Lam., Cavolina, Abitdg. 



Two large wingsj no tentacula,- a mantle cleft on the sides, lodging 

 the branchiae in the bottom of its fissures, and invested by a shell 

 also cleft laterally, the ventral face of which is arched, and the dor- 

 sal flat and longer than the other; the transverse line which unites 

 them behind, furnished with three sharp dantations. When alive, 

 the animal thrusts several appendages, that are more or less long, 

 through the lateral fissures of its shellj they are productions of the 

 mantle. 



B. cornea, Lam.; nomia tridentata, Forskahl.,- Cavolina nu- 

 tans, Abildgaard; Cuv., Ann. du Mus., IV, pi. 59; and Peron, 

 lb., XV, pi. 3, f. 3. A small, yellowish, semi-diaphanous shell, 

 found in the Mediterranean and the Atlantic Ocean(2). 



Cleodora, Peron. 



The Cleodorae, for which Brown originally created the genus Clio, 

 appear to resemble the Hyalese in the simplicity of their wings and 

 in the absence of tentacula between them; it is also probable that 

 their branchiae are concealed in the mantle; their conical or pyra- 

 midal shell, however, is not cleft on the sides. M. Ray distin- 

 guishes 



Cleodora, properly so called, with a pyramidal shell, 

 Creseis, with a conical and elongated shell(3), 



(1) 1 am not sure that the animal drawn by Scoresby, of which de Blainville 

 (Make, pi. xlviii, bis, f. 5) makes his genus Spirateiia, is, as he thinks, the 

 same as those of Phips and Fabricius. 



(2) Add: Hyal. lanceolata, Lesueur, Bullet., des Sc. June 1813, pi. v, f. 3; 

 Hyal. injlexa, lb., f 4. 



N.B. The Glaums, Carinaire, and Firole, referred by Peron to the family of the 

 Pteropoda, belong to the Gastekopoda; the PhilUroe of the same author also 

 probably belongs to it. His CallianYre is a Zoophyte. 



(3) It is probably near the Creseis, and perhaps even in the same subgenus, 

 according to Messrs Rang and Audouin, that we must place the genus Tripteua 

 of Messrs Quoy and Gaymard, which is referred by M. de Blainville to the family 

 of the Akerae. 



