T. XIIl] - CRUSTACEA CASPIA. 467 



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 lamellae 

 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 maxillae (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 setae of unequal size, both edged with fine recurved 

 hairs. 



The 2nd pair of maxillae (fig. 9) are semimembranous, and rather diffe- 

 rent in shape from the 1st pair. The basal part consists of 2 segments, the 

 1st 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 setae, and has the inner edge some- 

 what expanded, and provided with a dense series of delicate curved setae. 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 

 biarticulate palp. Outside, the basal part forms a very thin lamellar expan- 

 sion, which perhaps maybe regarded as an imperfectly developed exognath. 



Bulletin N. S. IV (XXXVI) p. 303. 



