30 COLPODASPIS. 
The foot, upon this interpretation, must accordingly be described 
as T-square shaped, with gracefully arched anterior wings and 
rounded extremities, and of about the same length as the shell-bear- 
ing portion of the mantle. The median furrow of its plantar surface 
is shown in my drawing (fig. 2) to have the same extent as in Sars’ 
specimens. 
The Head.—The grooved tentacles in my opinion correspond with 
Sars’ description, except that no mention is made in the latter of a 
low curved ridge which can be seen in my figure 1 crossing the ante- 
rior part of the head from side to side and connecting the postero- 
dorsal edges of the two tentacles with one another. The eyes also 
are much closer together in the Plymouth individual than they are 
represented to be in Sars’ figures; and the statement of the latter 
that they are situated “close behind and within the base of the 
tentacles’? cannot be said to be applicablein the present case. Ido 
not, however, think that any great importance should be attached 
to those slight discrepancies. 
When Oolpodaspis pusilla is creeping upon a flat surface, the 
antero-lateral horns of the foot are just perceptibly in advance of 
the tentacles (fig. 1); but when the creature is swimming inverted 
at the surface of the water the tentacles are then seen to be consider- 
ably in front of the horns of the foot (fig. 2). 
The Body.—I have no addition to make to Sars’ account of the 
body proper, except that in the Plymouth specimen the edges of the 
pallial siphon were more closely opposed than seems to have been 
the case with Sars’ individuals. . 
Pallial appendage-—W hen the animal is creeping upon the bottom 
of a vessel, a broad flattened tail-like appendage projects behind the 
mantle and seems at first sight to be the posterior section of the 
foot. Examination of the animal from the ventral aspect, how- 
evers, reveals that this appendage is in reality a posterior prolonga- 
tion of the hinder margin of the mantle to the morphological left of 
the pallial siphon (fig. 2). 
In Philine catena also, according to Roulé, the mantle terminates 
posteriorly in a convex margin, a little below which are two fleshy 
prolongations, “which can be mistaken for the posterior border of 
the foot when the animal is contracted.” His figures unfortunately 
do not show this point at all well (pl. i, fig. 25), and Forbes and 
Hanley’s figure, though clearer, does not seem to represent the 
anatomical relations correctly (1. e., pl. UU, fig. 4.) 
