M. Souleyet on the Gasteropod Mollusca. 347 



has given only a very insufficient description ; I can however only 

 indicate here briefly the errors which he appears to me to have 

 committed. 



1 . Contrary to the assertions of this naturalist, the Acteon has 

 a heart, an arterial system, &c; in a word, a complete apparatus 

 of circulation which has much analogy with that of the Eolides. 



2. The dorsal pouch which M. de Quatrefages has considered 

 as the stomach, and from which proceed the ramified canals which 

 cover, above, the lateral expansions of the animal, has no com- 

 munication with the digestive tube; it is a distinct apparatus 

 which opens externally by a peculiar orifice placed behind that of 

 the anus, and which seems to serve for the respiration in this 

 mollusk. In the same way the ramifications of this apparatus 

 have no communication with the vesiculous ampulliform organs, 

 which thus in no way present the regular position which this na- 

 turalist assigns to them in his figures. 



3. The whole digestive tube, from the buccal cavity, the de- 

 scription of which likewise differs from my investigations, appears 

 to have escaped the observation of M. de Quatrefages. 



4. The position which M. de Quatrefages assigns to the anus, 

 at the posterior and median portion of the body, is certainly inac- 

 curate ; there is at that point neither orifice nor cloacum. The 

 anal aperture is situated at the anterior and dorsal part of the 

 animal on the right side, and always occurs in the form of a 

 small protuberance, which is easy of detection. 



5. The genital orifice is not simple, and has likewise a differ- 

 ent position to that which M. de Quatrefages assigns to it ; the 

 aperture of the oviduct is on the right side, in a small groove 

 which descends from the anus towards the lower surface of the 

 animal j that of the male organ is situated on the same side, at 

 the base of the tentacle. 



My observations on the zoological characters of Acteon agree 

 entirely with those which have been communicated to me by M. 

 Verany of Genoa, who has often had opportunities of observing 

 this small mollusk. 



M. de Quatrefages has given no detail on the reproductive ap- 

 paratus of Acteon ; but he appears to say that the arrangement 

 of that apparatus is the same as that which he indicates in a suc- 

 cinct manner in his genus Acteonia : in that case, I might still 

 affirm that the organs of generation in Acteon have no analogy 

 with the description which is given by that naturalist. 



I can say nothing of the genera Acteonia, Placobranchus, 

 Pelta and Chalidis, which are also included in the order of the 

 Phlebenterate Mollusca of M. de Quatrefages, not having been 

 able as yet to procure these mollusca. But of these genera, the 

 first or Acteonia does not differ from Acteon, according to this 



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