778 CLASS xin. 



Sp. Atlanta Peronii LESUEUB, Corne d'Ammon LAMANON, Voyage de LA 

 PEYEOUSE, PL 63, figs, i 3, BLAINV. Malac. PL 48 bis, fig. 9; Atlanta 

 Keraudrenii LESUEUR; this species forms the genus Ladas CANTRAINE, 

 Malacol. m&diterr. Compare on these small animals that occur in the 

 Mediterranean and in warm zones of the Atlantic Ocean, RANG Mem. de 

 la Soc. d'Hist. not. Tom. in. 1827, pp. 372 380, PL 9, and D'0-RBIGNY 

 Voyage (see OKEN'S Isis, 1839, pp. 511 519). 



B. Gasteropoda normalia. 



Foot serving for creeping, flattened or grooved. 



Section I. In some no distinct organs of respiration, in others 

 naked dorsal branchiae, appendages or various productions of the 

 common integuments. 



We part the common or normal Gasteropods into three divisions, accord- 

 ing to their respiratory organs, and unite, as was proposed by the younger 

 LEUCKART, the Gymnobranchiata and Apneusta under the name of Derma- 

 tobranchiata of DUMERIL ; see K. LEUCKART Ueber Morphologic der wirbell. 

 Thiere, 1848, s. 178. 



Family IV. Dermatobranchiata s. Crymnobranchiata. Cha- 

 racters of the section. Naked Gasteropods, hermaphrodite, marine, 

 often swimming on the back, with foot supine. 



The Nudibranchiates (nudibranckes) of CUVIER have been espe- 

 cially investigated in the latest times. By QUATREFAGES, in many 

 an intestinal canal divided into branches was discovered, or rather a 

 branching appendage of the same, such as we have already noticed 

 in Distoma, in some ringed worms, in Acarina, in Phalangium, &c. 

 These blind branches discharge at the same time the office of liver. 

 (QUATREFAGES gave to this arrangement the name of Phlebenterismus 

 (see Ann. des Sc. nat., Sieme SeYie, Tom. iv. p. 83), which has caused 

 much misconception.) In some it would seem that no heart is 

 present ; whilst there are such conflicting opinions on this point, we 

 consider it inexpedient to found an arrangement upon it, which 

 might afterwards be subverted, and therefore cannot adopt the 

 families of Anangia and Angiophora (V. SIEBOLD Lehrb. d. vergl. 

 Anat. i. s. 297). As little do we feel ourselves justified in sepa- 

 rating the Apneusta from the Gymnobranchiata. Those Gasteropods 

 alone can be regarded as Apneusta, which, as Lissosoma, have no 

 external dermal appendages. 



Compare ALDER and HANCOCK in different parts of the Annals and 

 Magaz. of Nat. Hist., and their Monograph of the British Nudibranchiate 



