120 MESSES. NOKMAN AND STEBBING ON THE 



other times partially coalesced ; at other times, again, they are all distinctly separated. 

 The telson is linguiform, rarely lanceolate, with the termination rounded or 

 truncate. 



The upper antennee are situated at the exterior angle of the head, and the lower take 

 a very unusual position in having their bases closely appressed together, and occupying 

 a central position between and below the origin of the upper pair. The upper pair 

 consist of a three-jointed peduncle and short, sometimes rudimentary, flagellum in the 

 female ; but in the male the flagellum is, in some species, enormously developed into 

 a long brush-like appendage as long as half the animal, and composed of very numerous 

 and thick articulations, which are densely setose. The lower antennae consist of a 

 five-jointed peduncle and short flagellum. The mouth-organs are all formed to serve 

 purposes of perforation and of suction, and not of mastication ; these organs, as they 

 exist in Cyathura carinata, Kroyer, have been minutely and admirably described and 

 figm-ed by Schiodte ^. In this and allied forms the mandible is apparently used as a 

 saw, the outer portion of the jaw being strong, slightly dentate at the extremity, and 

 giving support to a semicircular under portion, which is finely serrate on its sharp 

 edge, while the first maxillae are somewhat pyriform, the base being the thicker portion, 

 and the extremity is again moderately expanded and terminates in rows of four or five 

 teeth. But in a second group of this family (Paranthura) the mandible is aciculate, 

 terminating in a single styliform point, with the under portion of delicate structure 

 and sharp unserrated edge, the whole being evidently used as a lancet ; and the 

 first maxillae are spear-like, very long and slender, with the distal edges finely 

 toothed. 



The first gnathopods have strongly developed basos and ischium, the meros short 

 but wide, the carpus minute and triangular ; the propodos pear-shaped or more or less 

 triangular, its base very wide, attached to the carpus, but its upper portion, as a 

 rounded lobe, rests on and finds support from a cup-like receptacle in the expanded 

 portion of the meros. The dactylus is usually as long as the palm of the propodos, on 

 which it closes. 



The second gnathopods and first peraeopods are usually alike in structure, and in 

 general form resemble the first gnathopods, but are much more slender. The 

 remaining peraeopods are constructed for walking. 



The first pleopods have the outer rami greatly developed, and these together form a 

 kind of operculum, which in the female reaches to the extremity of the five first 

 segments of the pleon, and conceals and protects the remaining pleopods which lie 

 beneath it. 



The uropods have an arrangement which is unique among Crustacea, inasmuch as 

 the outer ramus, which has only a single joint, instead of, as is usually the case, arising 



■ " Krebsdyrenes Sugemund," Naturhistorisk Tidsskrift, 3 R. 10 B. (1875), p. 211, tab.iv. 



