(xxxv1)] CRUSTACEA CASPIA. 303 
The posterior lip (fig. 6) is quite membranous, consisting of 2 somewhat 
securiform lobes, united at the base, and finely ciliated along the inner edge 
and the obtusely rounded tip. 
The mandibles (fig. 7) are rather slender, but strongly incrusted, and, 
as usual, without any trace of a palp. They consist each of a navicular body, 
terminating above in a point, and 2 diverging branches issuing from the 
lower extremity of the body, and constituting together the masticatory part. 
The outer branch, which forms the immediate continuation of the body, is 
somewhat compressed, and terminates with 2 slightly dentated lamellæ 
forming the cutting edge; behind these plates are affixed to the inner edge 
of the branch 5 slender and curved spines ciliated on the one edge. The 
inner branch, constituting the molar expansion, issues at a right angle from 
the body, and is rather massive, cylindrical in form, and terminates in a 
finely fluted triturating surface. 
The 1st pair of maxillæ (fig. 8) each exhibit a rather thick and mus- 
cular basal part, from which issue anteriorly 2 masticatory lobes, and 
exteriorly a peculiarly modified palp. The outer masticatory lobe is somewhat 
compressed, and tapers a little towards the tip, which is obliquely truncated, 
and armed with numerous strong spines. The inner masticatory lobe is much 
smaller than the outer, and of membranous structure, with the inner corner 
produced to a conical projection, to the end of which are affixed 4 ciliated 
spines successively increasing in length posteriorly. The palp, which origi- 
nates from the exterior side of the basal part, at the insertion of the outer 
masticatory lobe, is turned straight backwards, projecting within the 
branchial cavity. It consists of a single somewhat cylindrical joint, in the 
interior of which a strong muscular band is visible, and carries on the tip 
2 diverging band-like setze of unequal size, both edged with fine recurved 
hairs. 
The 2nd pair of maxillz (fig. 9) are semimembranous, and rather diffe- 
rent in shape from the 1st pair. The basal part consists of 2 segments, the 
Ist of which is very short, whereas the 2nd is rather expanded. It is conti- 
nued anteriorly in a short and broad, obliquely-truncated masticatory lobe 
carrying a row of short, densely-ciliated setze, and has the inner edge some- 
what expanded, and provided with a dense series of delicate curved sete. On 
the inferior side, at the base of the masticatory lobe, are seen 2 juxtaposed 
linear lappets pointing anteriorly, and carrying at the tip a number of curved 
bristles. On a closer examination, the outer lappet is found to be articulated 
to the base of the inner, and both together would thus seem to constitute a 
biartieulate palp. Outside, the basal part forms a very thin lamellar expan- 
sion, which perhaps may be regarded as an imperfectly developed exognath. 
Mélanges biologiques. T. XIII, p. 467. 
