502 
PAUL PELSENEER. 
have been able to assure myself with certitude that the second 
pair of tentacles positively exist in this genus, as with Clione 
and Clionopsis. But I have not remarked that they had 
the bifid form indicated by Souleyet. 1 These tentacles bear at 
their free extremity an eye, which has the same structure as 
those of the two preceding genera. 
b. Acetabuliferous Buccal Appendages. 
These appendages are inserted on the internal wall of the 
buccal cavity, on the ventral side. Two figures of Souleyet 
show this disposition perfectly (loc. cit., pi. 15, figs. 17 and 
30) ; fig. 17 has been badly understood by Fischer, who gives 
the two groups of suckers for the jaws. 2 
The acetabuliferous appendages of Pneumodermon have 
the form of a flattened cylinder, upon which are inserted the 
peduncles of the suckers. These vary in number according to 
the species. Pneumodermon Peronii possesses a large 
number of them, about thirty on each appendage; P. viola- 
ceum, ten to fourteen on each appendage, and P. mediter- 
raneum five or six. However, in this last species I have 
sometimes found seven suckers, but then one or two were very 
small. 
In the state of inactivity the suckers have the form of a 
very flat porringer. It is in P. mediterraneum that I 
saw the largest ; they were one line in diameter. 
Structure of the Acetabuliferous Buccal 
Appendages. 
It does not at all resemble that of the buccal cones of 
Clione. The whole of its mass is formed by longitudinal 
muscular fibres. Externally we find a uniform epithelium ; 
that is to say, it is not provided with sensorial cells like the 
epithelium of the cones of Clione. The buccal appendages of 
Pneumodermon are not, then, sensorial organs, as some 
1 Loc. cit., vol. ii, p. 256. 
5 Fischer, ‘ Manuel de Conchyliologie,’ fig. 42, p. 44. 
