GASTEROPODA PECTINIBRANCHIATA. 
77 
locomotion, is deprived of a foot, properly so called ; but the part 
which in ordinary Gasteropoda forms the tail, is here turned under 
it, and extends to beyond the head, where its extremity becomes 
inflated and furnished with a thin operculum ; when the animal 
withdraws into its shell, it is this mass which closes the entrance ; 
it is sometimes seen with various appendages, and in certain species, 
the operculum is spiny. The head of the animal is obtuse, and has 
two moderate tentacula, on the external sides of which, "at the base, 
are the eyes. The mouth is a vertical orifice, beneath which is a 
filament on each side, that has all the appearance of a tentaculum, 
but belonging in reality to the foot. The branchiae form but a single 
range along the left side of the roof of the branchial cavity. The 
right side is occupied by the rectum and the spermatic canal, which 
also transmits the ova. There is no penis, the animal fecundating 
itself. 
The species are numerous, but not very distinct. Linnaeus 
left them among the Serpulte* * * § . 
The Vermilice, also left by M. de Lamarck near the Serpulae, are 
similar to the Vermetif. 
Magilus, Montf., 
The Magili have a longitudinally carinated tube, which is at first 
regularly spiral, and then extends itself in a line more or less straight; 
although the animal is unknown, it is highly probable that it should 
be placed near the Vermeti J. The 
SiLIQUARIA, Brilg. 
Resembles Vermetus in the head, the position of the operculum, and 
in the tubvdar and irregular shell; but there is a fissure on the whole 
length of this shell which follows its conto>ir, and which corresponds 
to a similar cleft in that part of the mantle which covers the branchial 
cavity. Along the whole side of this cleft is a branchial comb, com- 
posed of numerous, loose and tabular-like lamellae. Linnaeus left 
them with the Serpulae, and till very lately they were considered as 
belonging to the class of the Annelides§. 
* Serpula lumhricalis, L., Adans., Senegal, XI, 1, and several new species. 
•[' Serpula triqueira, Gm., Born., Mns., pi. xviii, t. 14. 
I Magilus untiquus, Montf. II, pi. 43, and Guettard, Mdm., Ill, pi. Ixxi, f. 6. 
§ Serpula anguiaa, L.; — Serpula muricata, Born., Mns., XVIII, 16. 
N.B. M. dc Lamarck considered the Siliquariai and the Vermilire as neighbours 
of the Serpulae. M. dc Blainville has approximated them to the Verraeti ; M. An- 
douiii has lately observed and described the animal, and to him do we owe what is 
stated above. 
