Mr. C. Spence Bate on a new Species of Spheroma. 29 
which is very short and round; the third is twice as long as the 
second, but much shorter than the first, and the flagellum gra- 
dually tapers to an obtuse point, and is formed of several arti- 
culi, of which the first is much the longest. The inferior an- 
tenn are subequal with the superior, being perhaps slightly 
longer. 
The mandibles are robust, and furnished with strong pointed 
incisor teeth as well as a powerful molar tubercle, between 
which exists a process armed with six or seven strong, equal- 
lengthed, serrated spines, which are probably used in the tearing 
down of the wood into which the animal burrows. The se- 
condary appendage to this organ is short and three-jointed; the 
third joint is the shortest and is nearly as broad as long; it 
is ciliated upon the flexile margin with hairs, which gradually 
increase in length towards the apex of the appendage. 
The maxilliped, or third siagonopod, consists of five joints, 
of which the basal is longest and broadest, and carries the other 
four as an appendage, in this somewhat resembling the form of 
the second pair of gnathopoda in the Crabs. 
The two pairs of gnathopoda and the first pair of pereiopoda 
resemble each other in form and size. They are slender and 
comparatively feeble appendages, and furnished on the anterior 
margin with long plumose hairs—suggesting, from their simi- 
larity of feature with the same appendages in Arcturus, that the 
latter is not such an anomalous Isopod as some carcinologists 
have supposed ; the coxa is fused with the dorsal portion of the 
somite, and forms an overhanging lateral plate-like process; 
the basis and ischium are long and slender, and the latter is 
furnished with a thick row of plumose hairs on the anterior 
margin, which stands at right angles with the joint; the meros 
is short, anteriorly produced to a point, and furnished with a 
row of plumose hairs similar to the preceding; the carpus and 
propodos are short, slender, and furnished with short cilia on 
both anterior and posterior margins; the dactylos is short, 
curved, unguiculated, and armed with a small subapical tooth 
or secondary unguis. 
The last four pairs of pereiopoda resemble each other in ge- 
neral form; they are very robust and strong, and are furnished 
on the anterior and posterior margins with rows of stout bushy 
hairs, which appear to increase in number and strength poste- 
riorly, and some of which take a spinous character in the last 
two pairs, as on the distal extremity of the propodos, where they 
become spines with serrated margins. 
The first three pairs of pleopoda consist of a broad basal 
supporting an inner and an outer plate, the former of which is 
broadest at the base and ciliated at the apex; the latter is pear- 
