THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



No. 104. SEPTEMBER 1845. 



XIV. — On the Anatomy of Actseon, with remarks on the Order 

 Phlebenterata of M. de Quatrefages. By Geo. J. Allman, 

 M.B., F.R.C.S., M.R.I.A., Professor of Botany in Trinity Col- 

 lege, Dublin, late Demonstrator of Anatomy T.C.D.* 

 [With three Plates.] 

 In the seventh volume of the ' Linnsean Transactions ' is a memoir 

 by Colonel Montagu, in which is described, under the name of 

 Aplysia viridis, a small gasteropod discovered by this naturalist on 

 the coast of Devonshire. The Aplysia viridis of Montagu was 

 afterwards separated by Oken from the true Aplysias, and made to 

 constitute a distinct genus under the name of Actaon. A moUusk 

 evidently referable to the same genus is named Aplysiopterus 

 neapolitanus by Delle Chiaje, who describes and figures it in his 

 great work on the Invertebrate animals of the kingdom of 

 Naples. The Italian naturalist gives some details of its anatomy, 

 but his account is manifestly full of errors, and he seems to 

 mistake the ramified apparatus in connexion with the stomach 

 for a vascular system. A mollusk also apparently referable to 

 Oken's genus Actaon is described in the ' Faune d^Europe Sep- 

 tentrionale ' of Risso, under the name of Elysia timida ; and iXiore 

 recently M. de Quatrefages (Ann. des Sci. Nat. March 1844) has 

 published a very elaborate description of the genus, in which he 

 advances some new and startling views to which he had been pre- 

 viously led by the examination of Eolidina, a small nudibranch, 

 apparently an Eolis, but for the reception of which this naturalist 

 believes it necessary to construct a new genus. The claims of 

 M. de Quatrefages' opinions to reception by naturalists will be 

 considered in the present paper. 



The following anatomical details have been drawn up from 

 careful dissections of Actaon viridis, and as no figure which we 

 have seen represents with sufficient accm-acy the external cha- 

 racters of this little mollusk, we have thought it necessary to give 

 among the illustrations of the present memoir a drawing made 

 with great care from the living animal. 



* Read before the Meeting of the British Association at York, Sept. 1844. 

 Ann. ^ Mag, N. Hist, VoLxvi. M 



