14 oc. BOVALLIUS. REMARKS ON THE GENUS CYSTEOSOMA. 
The fifth pair of pereiopoda are three times longer than the 
seventh pair, and a little longer than the whole animal. 
The segments of the urus are not carmated. 
The peduncles of the last pair of uropoda are scarcely 
twice as long as the outer rami, narrower than the length 
of the rami. The outer ramus is a little longer than the inner. 
Through the long and coarsely denticulated legs this 
species is easily distinguished from the others. 
The head is nearly globular, very tumid. From the ante- 
rior end a little beyond the bases of the antenn&e runs back- 
wards on each side a row of about 20 small spines, situated 
as in the next preceding species. 
The eyes occupy the upper surface of the head, not unit- 
ed on the median line. 
The first pair of antenne are fixed at the anterior end 
of the head, a little above the row of spines. They consist 
of two joints, the first short, a little tumid, the second very 
long, feebly arched, serrated along the margins, without bristl- 
es or glands. (Fig. 16). 
The second pair of antenne consist of two sharp-pointed 
tubercles, on the underside of the head, closer to the mouth 
than to the anterior margin. 
The mouth-organs are similar to those of Thaumatops 
Lovéni. 
The segments of the pereion are not very much inflated. 
The first and second segments are much deeper than the follow- 
ing; the first is deeper than the second but much shorter 
(4: 0)5 the seventh segment is shorter than the second. A 
ridge indicating the NT exists on the five last pereional 
std. on all the pleonal segments. This ridge is totally smooth. 
On the dorsal side is a keel with spine-like tubercles on all 
the pereional segments. This keel continues on the pleon, 
where it is feebly spinulous. Near the posterior margins 
of the second, third and fourth pereional segments run down- 
wards a row of very small tubercles, the posterior margins of 
the fifth, sixth and seventh, even as the two first pleonal 
segments are bordered with minute spines. (Fig. 15). 
The first pair of pereiopoda (Fig. 17) are about a fourth of 
the length of the third pair. The femur is longer than the 
following joints together, almost linear, with three denticulations 
