778 CLASS XIII. 
Sp. Atlanta Peronti Lusunur, Corne d’Ammon LAMANON, Voyage de La 
Pryrovuse, Pl. 63, figs. 1—3, Buatnv. Malac. Pl. 48 bis, fig. 9; Atlanta 
Keraudrenii Lesvevr; this species forms the genus Ladas CANTRAINE, 
Malacol. méditerr. Compare on these small animals that occur in the 
Mediterranean and in warm zones of the Atlantic Ocean, Rane Mém. de 
la Soc. d’ Hist. nat. Tom. 111. 1827, pp. 372—380, Pl. 9, and D’ORBIGNY 
Voyage (see OKEN’S Isis, 1839, pp. 511—5§19). 
B. Gasteropoda normalia. 
Foot serving for creeping, flattened or grooved. 
Section I. In some no distinct organs of respiration, in others 
naked dorsal branchiz, 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 
Levuckart, the Gymnobranchiata and Apneusta under the name of Derma- 
tobranchiata of DuM&RIL; see R. LEvcKart Ueber Morphologie der wirbell. 
Thiere, 1848, s. 178. 
Family IV. Dermatobranchiata s. Gymnobranchiata. Cha- 
racters of the section. Naked Gasteropods, hermaphrodite, marine, 
often swimming on the back, with foot supine. 
The Nudibranchiates (nudibranches) 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 Phalangiuwm, &e. 
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., 3ime Série, Tom. rv. 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. Strsotp Lehrb. d. vergl. 
Anat. 1. 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 
