CRUSTACEA MALACOSTRACA. III. 



93 



anterior ends of the keels limiting the front area (fig. 4 a), and the short anterior margin of this area 

 is concave. — Anteunulse (fig. 4 c) in the main as in A", simplex; first joint somewhat longer than 

 broad; second joint slender, a little longer than the first, with its terminal processes nearly as long as 

 broad; the process of fourth joint reaches beyond the middle of the pyriform vesicle; the foot of each 

 of the long setse on second joint oblong. — Antennal sqnama not marked off at its base, longer than 

 in any other species, excepting X. casphis G. O. S., from a little (fig. 4 c) to considerably or much (fig. 411 

 longer than the diameter of third joint. 



Second thoracic segment (fig. 4 a) with a moderately short spine on the antero-lateral angles, 

 while the corresponding angles of first and third segments have a fine or stiff, short seta. The posterior 

 ventral median part of the thorax raised as a high and broad, rounded protuberance, which lies close 

 to the front end of the abdominal operculum, and has no process. — The legs nearly as in 3". simplex. 



Abdomen with the lateral margins somewhat convex and converging (fig. 4 e), and the post- 

 erior margin moderately broadly rounded at the end. — Operculum about as long as broad, with the 

 posterior margin nearly straight or even slightly concave, while the median proximal part of the lower 

 surface is much vaulted and armed with a recurved, acute process. — Uropods with the peduncle 

 oblong, the endopod thicker and very considerably longer than the exopod. 



Length of full-grown specimens 2 — 26 mm. 



Male. Body about three and a half times as long as broad, with the anterior part of the 

 thorax a little broader than the posterior. — The head is nearly nine times as broad as the distance 

 between the anterior angles of the keels limiting the front area (fig. 4 b), as the keels converge strongly, 

 and protrude conspicuously with their acute ends. — Antennulae and proximal joints of the antenna: 

 as in the female (the antennal flagella lost). Thoracic legs as in the female, excepting that the 

 three posterior pairs have natatory setse on fifth and sixth joints as in the male of N. simplex. (In a 

 very young male, im mm. long, the natatory setse were wanting). 



Abdomen differs in outline from that of the female, as its median posterior part is produced 

 backwards (fig. 4 d) with the end somewhat narrowly rounded, and the margins somewhat before this 

 end are distinctly concave. — Operculum a little longer than broad; the median lamella a little widened 

 towards the end, with each outer angle produced into a triangular tooth directed backwards and a 

 little outwards, while the major terminal part of the lamella constitutes a kind of lobe with the hind 

 margin semicircular. — Uropods with the peduncle distally somewhat produced, otherwise nearly as 

 in the female. 



Length of the largest male 2 - 2 mm. 



Remarks. A*, obloiigits is easily separated from A', urctieus and N. analis in having consider- 

 ably shorter distance between the anterior ends of the keels on the head, and the squama considerably 

 longer; from A*, simplex it is instantly distinguished in having spines on the antero-lateral angles of 

 second instead of first segment. 



As mentioned above, there is in the females some variation in the distance between the end 

 of the keels of the front area and in the length of the squama. In most females from Stat. 78 the 

 distance mentioned (fig. 4 a) is shorter than in specimens from Stat. 32, and it is still longer in some 

 specimens from Norway. As I was not quite sure that my reference of the "Ingolf ' specimens to A 7 ! oblongits 



