258 PATELLID A. 
the upper surface there are three other lead-coloured bands, 
varying in breadth; the one immediately above the foot is 
narrow and faint; the next is the broadest, and takes the 
shape of the circular muscle, distinctly shadowing out its 
strong, thick-set, transverse muscular filaments; the upper- 
most is narrow, and the most intense in colour. The mantle 
within is white, and between its margin and the body is placed 
the branchial cordon of 80-100 white subtriangular plates, 
margined at the outer edges, and so extremely close-set as to 
present the appearance of mere thread-like filaments without 
depth ; these line #ths of the circumference, passing round the 
posterior end, where they are largest, diminishing gradually 
anteally, until they are interrupted by the head. 
I am of opinion with Professor Forbes, that this cordon is 
only an elongated branchial plume springing from the neck, 
and ought not to be looked on as a pair of symmetrical sub- 
semicircular lamin, as in the cyclobranchiate Chitons. I 
think this view is confirmed by the animal having the ven- 
tricle accompanied by only one auricle instead of two, as 
in Chiton. The heart and auricle does not span the in- 
testine, as in nearly all the Bivalves, and in the last section. 
This is a remarkable departure from the usual structure, 
and indicates an approach to the more advanced Gastero- 
poda, and pomts out that Patella ought to follow Fissurella 
and Emarginula. The head is a plain subcireular muzzle, 
under which is the oval, puckered, hollowed-out mouth with 
a vertical fissure; and, within, the corneous plates may be 
seen, supporting the lead-coloured palate, and the very long, 
narrow, light yellow spinous tongue passing through the 
cesophagus, that is spirally coiled in the stomach, which 
pursues its course as an intestme, with many circumvolu- 
tions entwined with the liver, which in this species is a 
hight green granular mass; near the posterior end it doubles, 
and, accompanied by the oviduct, terminates a little to the 
right of the neck under the tentaculum, and not, as is more 
usual, lower in the side of the body, and more posterior ; 
the anal tube and the oviduct march together to the right 
side, the former being double the size of the latter. The ten- 
