JRA. 315 
mandibles are strong, horny, curved inwards at the tip, 
and armed with several teeth, the lowest of which is 
truncate. They are provided with a three-jointed palpi- 
form appendage. The basal joint of the foot-jaws is 
large and triangular, with the tip ciliated, followed by 
five joints, of which the distal ones are the most slender. 
The first pair of maxille are furnished at the extremity 
with three oval membranous plates, ciliated at their 
extremities, the anterior one being the largest. The 
second maxillz are composed of two branches, of which 
the outer one is the larger, and armed at the tip with 
strong bearded bristles. 
The segments of the body are strongly marked by 
lateral incisions, the sides being rounded, and the pos- 
terlor-lateral margins not produced into a point. The legs 
are of moderate size, being nearly uniform both in length 
and thickness, and terminated by two small hooks of 
nearly equal size. The female carries between the base 
of the legs an ovigerous pouch, composed of delicate 
membranous plates, within which the young are deve- 
loped. The tail consists of only a single plate, formed by 
the coalescence of all the segments of the pleon, which is 
semicircular (or semi-ovate) in form, and,in our British 
species, with a small semicircular incision in the middle 
of the posterior margin, within which are attached the 
two very minute terminal appendages, each of which 
consists of a square flat joint, supporting two extremely 
minute conical plates, of which the outer one is almost 
obsolete; the tips of these plates are furnished with 
hairs. In J. Kréyerii the tail has two small semicircular 
incisions, between which the centre is produced into a 
small point, and the appendage on each side consists of a 
small square basal joint, supporting two minute oval 
plates. 
