CRUSTACEA MALACOSTRACA. III. 181 



Cyathura Norman & Stebbing. 



The type is C. carinata Kroyer. Its mouth-organs have been studied by Schiodte (1875) and 

 by Norman & Stebbing (1886), but a few corrections may be given for comparison with the structure 

 in my new species C. truncata. Norman and Stebbing described and figured the maxillipeds as three- 

 jointed, but they have overlooked the basal joint and the epipod ; Schiodte overlooked the basal joint 

 and figured the epipod, but interpreted it wrongly. The authors have overlooked the inner lobe of 

 the maxillulse, which is developed as in C. truncata to be described presently; as to the maxillae these 

 must be very reduced or wanting, and the organ described by Schiodte as the maxillae is in reality a 

 part of the paragnatha. 



The generic characters may be pointed out. The antennulse (fig. 2 a) have the flagellum reduced, 

 two-jointed, the terminal joint tiny. The antennae have the peduncle five-jointed, with second joint large, 

 but whether this joint is formed by the fusion of two joints cannot be decided; the flagellum in the 

 females is moderately short or very short (in C. carinata it seems in the females to consist of a single 

 small joint, but a closer examination under high magnifying power revealed that joint as subdivided 

 into four joints, the three distal extremely short). Labrum rounded. Mandibles with some rounded 

 teeth on the cutting edge, and behind that edge a large plate with the thin and convex inner margin 

 distinctly or — in C. truncata (fig. 2 c) — indistinctly serrate. Paragnatha (fig. 2 d) with the two lobes 

 obtuse and setiferous, the median lobe broad and distally emarginate. Maxillulae (figs. 2 e and 2 f) with 

 the inner lobe distinct, short, terminating in a narrow free part with an apical seta, the outer lobe 

 with the oblique end produced into several slender, spiniform processes. Maxillipeds (fig. 2 g) five- or 

 (in C. carinata) four-jointed; the basal joint with its epipod well developed. — Second pair of thoracic 

 legs (fig. 2 k) feebly prehensile, as the sixth joint decreases a little in depth from near the base to the 

 end, with its lower margin a little concave. Seventh thoracic segment short. — Abdomen short, with 

 the five anterior segments coalesced on the median part of the upper surface (fig. 2 m). First pair of 

 pleopods (fig. 2 n) have the exopod developed as a large, solid plate covering the narrow endopod and 

 the other pleopods; second pair (fig. 20) with both rami unjointed, but the exopod has a vestige of a 

 division at the outer margin. Uropods broad ; the exopod (fig. 2 p, ex) is a large, oblong plate. Telson 

 (fig. 2 q) oblong, somewhat ovate, with a pair of statocysts beneath the dorsal wall a little from 

 the base. 



Of the two northern species known to me only C. truncata n. sp. has been found in the "Ingolf" 

 area. When Norman & Stebbing in enumerating the geographical distribution of C. carinata wrote: 

 "Greenland (Kroyer)", this must certainly, as already suggested by Meinert, be due to some misunder- 

 standing; Harriet Richardson (1905) reproduced this error of the English authors. — The females of 

 the two species may be separated by this key. 



Antennal flagellum consists of a joint (subdivided into four joints) much shorter than the ter- 

 minal joint of the peduncle. Mandibles with the inner margin of the incisive plate strongly serrate. 

 Maxillipeds four-jointed. Telson terminates in an obtuse angle. C. carinata Kroyer. 



Antennal flagellum at least as long as the terminal joint of the peduncle, seven-jointed, but 



