TROCHUS. 309 
same character as the capitular ones. There are two small, 
very dark, suboval head-lappets, situate at the inner sides of 
the tentacula. What are called the neck-lappets are only 
continuations of the operculigerous lobe, the one on the 
columellar side breaking into 8-10 long dentations ; the outer 
one is plain ; both are of a flake-white, mixed with pale green 
on both sides. 
The animal is littoral, and plentiful, though locally distri- 
buted. 
A singular character is attached to this species, which I 
have not observed in any other Trochus. The animal either 
casts the operculum, or is deprived of it by the attacks of 
enemies, perhaps from its own pulli, white masses of which, 
in the genial season, I have seen deposited on the foot, and 
they may possibly feed on and destroy it; however this may 
be, numerous examples are found with the opercula in various 
stages of development and renewal, but never resembling the 
original: this is a curious fact, which I can at present scarcely 
account for on rational grounds. The renewals and repara- 
tions form irregular spiral, oblique and elliptical curves, or, 
instead of the sixteen normal volutions, often only show two 
grossly spiral ones, as in the Littorina littorea. I have many 
such in my collection. I may observe, that, however the 
sculpture of the area may be varied, the operculum always 
retains the circular form. 
The species of this section that have not occurred in a 
living state are,— 
T. MILLEGRANUS, Philippi. 
T. millegranus, Brit. Moll. ii. p. 502, pl. 66. f. 9, 10. 
?'T. ataBastrum, Beck. 
T. alabastrum, Brit. Moll. ii. p.497, pl. 66. f. 7, 8. 
T. exicuus, Pulteney. 
T. exiguus, Brit. Moll. ii. p. 505, pl. 66, f. 11, 12. 
T. striatus, Linneeus.- 
T. striatus, Brit. Moll. i. p. 508, pl. 66. f. 5, 6. 
T. conutus, Linneus. 
T. conulus, Brit. Moll. ii. p. 495, pl. 73. f. 1, 2. 
