bo 
or 
b> | 
PATELLA. 
** With a single branchial leaf, and the heart and one auricle, not in 
contact with the intestine. 
This section of the Patellide comprises the typical Patelle, 
Acmea, Calyptrea, and Pileopsis, which have a single bran- 
chial plume, and all but symmetrical shells. 
PATELLA, Linnzus. 
P. peLLucipA, Linn. 
P. pellucida, Brit. Moll. ii. p. 429, pl. 61. f. 3,4; (animal) pl. A.A. f. 1. 
P. levis, Auctorum. 
Shell, an obtuse symmetrical cone of variable altitudes, 
with strize or fine ribs, and intense cerulean lines radiating 
from the vertex, which is anteal, to the basal periphery. 
Animal when young ovately convex ; when adult, subconical 
and often much depressed. As long as the shell maintaims 
the character of the “pellucida” of authors, it has a regular 
figure, but as soon as adolescence has passed, then the animal 
almost always begins to increase its circumference in a dif- 
ferent plane, the pellucidity diminishes, and the full-grown 
shell becomes opake, when it will be seen that the original 
form, styled pellucida, forms the subcentral vertex of the adult 
P. levis. This condition may be observed in most full-grown 
examples, and thus declares the identity of the two forms 
so emphatically, as to render it unnecessary to examine the 
animals for distinctive characters. It is difficult to conceive 
on what grounds they have been separated. I have, however, 
compared a large series, in all stages of growth, of the pellu- 
cidan animal with the P. /evis; it is almost needless to say, 
the organs are similar in every respect, allowing for the varia- 
tions of colour dependent on age. 
The mantle does not extend beyond the shell, except that a 
cordon of about 50-65 equidistant, rather long, extremely 
slender, sharp-pointed, white, tentacular filaments, proceeding 
from minute eminences contiguous to the fine lead-coloured 
line that borders its circumference, floats beyond the margin. 
These are so fine as to require a good lens to see them: on 
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