1 66 ON THE MORPHOLOGY OF THE CEPHALOUS MOLLUSCA 



2. The genus Psyche^ or Euribia offers a very interesting transition 

 from the foregoing to the second subtype. This genus is commonly 

 said to have a cartilaginous shell, but this so-called shell appears, upon 

 careful examination, to be only the thickened integument of the bod}' ; 

 it is not secreted by a true mantle, like that of Clcodora, &c. The 

 notion of a shell has arisen seemingly from the fact that a sort of cleft 

 exists anteriorly from which the locomotive organs of the animal can 

 be protruded and into which they can be retracted, but at the margin 

 of this cleft the softer parts of the body are continuous with the 

 harder, just as the body of a Polyzoon is connected with its cell. 



In some individuals I have observed the posterior extremity of the 

 body to be surrounded by two circlets of cilia.^ 



The head of the animal is provided with two very large tentacles,^ 

 which carry a large process upon the inner side of their base, and 

 rudiments of eyes upon the outer. Between the tentacles on the 

 ventral side are two projecting lips with the aperture of the mouth 

 between them, fig. 3. 



Behind the mouth there are two lobes, separated by a deep notch ; 

 these are the two portions of the mesopodium which had begun to be 

 separated in Ch'o. Behind these, again, there is a single tongue-shaped 

 lobe, the metapodium, which is continuous on each side with two elon- 

 gated and expanded epipodia. 



There are no gills, and the anus opens ventrall)^ upon the left side. 



From this genus, to that called Criseis by Rang, but which Eydoux 

 and Souleyet unite with Cleodora, the transition is very easy, figs. 6, 7. 



In these forms there is an elongated conical shell, narrow and 

 straight, or wider and slightly curved at its extremity. The body 

 puts one in mind of that of a Cephalopod, being enveloped in a wide 

 mantle, which is united to the body on the dorsal side only (fig. 6). 

 The wall of the mantle is very thick, so that it presents a wide aper- 

 ture always open upon the ventral side. Its free edge is, as it were, 

 cut down upon its dorsal side, so that ventrally it is considerably 

 longer. On the right side this prolonged portion has a rectangular 

 edge, but upon the left it forms a sort of ram's-horn process.* The 

 lower part of the inner surface of the mantle is richlj' ciliated, and 



^ My species appears to be the Eiirihia Gandichaudii of Eydou.x and Souleyet. 



- It is a very interesting fact that Professor Miiller has found the larvae of Pneitmodermon 

 to be provided with similar ciliated bands, Ueber die Entwickelungs-formen, &c. Monats- 

 bericht d. k. Akad. d. Wiss. zu Berlin, October, 1852. 



^ These are called "branchies" by Eydoux and Souleyet (pi. 15), but why I cannot 

 divine, since these organs are certainly homologous with the tentacles of Cleodora. 



■* Is this to be compared with the small posterior curved process of the edge of the mantle 

 in Gasteropteron ? 



