APPENDIX. 517 
8-10 cirrhi. The colowrs described are those of the animals 
examined; they vary greatly, and in individuals exhibit all 
the shades of red, pink, purple, brown, maroon, bistre-yellow, 
and all the greens. 
The foot is long and narrow, with a tumid aspect on the 
upper surface, rounded in front, without a trace of auricles, 
obtusely lanceolate at the posteal end, and marked above 
with red-brown, zebra-like, or narrow, longitudinal, wavy 
lines; the sole is yellow, having a central depressed line 
throughout its length, and is sometimes coasted on each side 
by a narrow, bistre-coloured stripe. The operculigerous lobe 
is almost co-extensive with the foot, of a dark red-brown 
colour, and largely alated; it is furnished with three densely 
ciliated, flattish, pomted vibracula on each side; the middle 
ones are very short and inconspicuous, each bifid, or formed 
of two strands: with powerful glasses I have never failed to 
discover them in all the Exmouth examples, and I believe 
that three on each side is the normal number. The lobe 
carries a white, highly polished, subcircular, testaceous pauci- 
spiral operculum, concave within, convex without, and fixed 
on the posterior extremity about midway. This animal has 
the peculiar littorean oscillatory quality of progression, which, 
with the paucispiral operculum, seem to mark it as a trans- 
ition genus from the Trochi to the Littorine ; we, however, 
must admit, that by the vibracula and neck-lappets it has 
a close connection with the Trochide. I am puzzled about 
the reproduction, on which account I can only at present 
refer to the original notes. No exserted verge has been 
detected, and though placed in our first account, provisionally, 
with the Trochide, 1 rather think, by the character of the 
operculum, it is bisexual, and that in a comparison of the two 
genera, the balance preponderates on the side of Littorina. 
It is sometimes infested with a longish, strong, cylindrical, 
dark brown parasite, with a clavate termination, which hangs 
to the side of the opercular lobe, and may be mistaken for a 
vibraculum. 
Cacum TRACHEA.—(P. 827.) 
The tentacula are not short, as originally stated, but com- 
