a 
CANCELLUS TANNERI. 53 
pilose. Behind the cervical groove the cardiac area is conspicuous as a cal- 
cified plate, rounded behind; on each side of the anterior part of the cardiac 
area there is a narrow, distinctly calcified area belonging to the branchial 
region ; aside from this the branchial areas are soft and membranous. ‘The 
abdomen is very short and obese, convex above in both directions, soft and 
clothed with a short velvety down, excepting the last three segments, which 
are calcified; the terminal segment or telson is broader than long, its sides 
regularly rounded, its hind margin nearly straight. The abdomen as a whole 
is not quite bilaterally symmetrical, the right side being more swollen than 
the left, a condition which gives the abdomen a slight twist to the left. 
The eye-stalks are slender, cylindrical, slightly curved inward, and some- 
what shorter than the anterior section of the carapace; the eyes are small, 
not broader than the eye-stalk, and of a dark brown hue. The opththalmic 
scales are triangular, short, acute, and produced to a prominent angle on 
the external side of the proximal end. The antennular peduncle is about 
one half as long as the eye-stalk ; it bears a short flagellum which reaches 
beyond the eyes by one half of its length. The antennal scale is short and 
triangular ; it ends in a small distal spine; the external margin is armed with 
three, the internal margin with two, small spinous teeth. 
The chelipeds are short, stout, and symmetrical. As in the other spe- 
cies of this genus, the upper surface of the propodite and anterior part of the 
carpus are flattened so as to form, when the right and left chelipeds are 
brought together, a facet, — the front wall of the operculum which closes the 
orifice of the cavity in which the animal dwells. The inner margin of each 
demi-facet is raised into a crest, whose margin is cut into closely approxi- 
mated quadrangular lobes by perpendicular fissures; the free margin of each 
lobe, moreover, is irregularly toothed; the whole upper and outer surface of 
the propodite is more or less rugose. The fingers are short and thick; they 
meet only at the tips, which are furnished with very large, horny, black 
nails; the opposed edges of the fingers are armed with coarse teeth; the 
movable finger is strongly curved and its surface is tuberculose ; both fingcrs 
are furnished with pencils of long and coarse bristles. The movable finger 
(dactylus) moves in a plane oblique to the plane of symmetry of the body. 
The superior face of the anterior part of the carpus, together with the cor- 
responding face of the propodite and dactylus of the second pair of legs, is 
flattened to form the external part of the operculum. As in the chelipeds, 
so here the margins of the opercular facet are cut into denticulated lobes ; 
