104 CRUSTACEA MALACOSTRACA. III. 



65. Nannoniscus spinicornis n. sp. 

 (PI. X, figs. 2 a-2 g). 



Female (not quite full-grown). Body even a little more than four times as long as broad, 

 with the anterior segments more arched and more deeply telescoped (fig. 2 a) than in any of the pre- 

 ceding species; second segment about one-third as broad again as the seventh, which is distinctly 

 broader than the front end of the fifth. 



Head conspicuously longer than usual in proportion to its breadth ; the cephalic keels very low, 

 scarcely converging anteriorly (fig. 2 a), without real anterior angles, but the distance between their 

 anterior parts is only a little less than half of the breadth of the head ; the anterior margin of the 

 front area is a little convex. - - Antennulse (figs. 2 b and 2 c) very peculiar ; first joint uncommonly 

 narrow, more than half as long again as broad ; second joint longer than the first, gradually increasing 

 considerably in thickness from the base to the end, which is produced into three long, oblong-triangular, 

 acute or subacute processes; the right antennula (fig. 2 b) drawn in its natural position shows only 

 two of these processes, as the third process is covered by the vesicle, furthermore only the outer part 

 of third joint is visible to the left, and the fourth joint itself is covered by the left process of second 

 joint, while the process of fourth joint is uncovered and is long, more than half as long as the ovate 

 vesicle. The left antennula had been turned in a different direction and, seen from above (fig. 2 c), 

 the three terminal processes of second joint are visible from above, the fourth joint lies between two 

 of these processes, and its major part is uncovered, but its process is completely covered. Antennse 

 lost, excepting its proximal joints; squama (fig. 2 a) small, broader than long, with the lateral margins 

 subparallel, and the terminal margin long, transverse. 



Antero-lateral angles of the three anterior segments scarcely or slightly produced, acute, but 

 spines or setse were not discoverable. Median ventral part of seventh segment (figs. 2 f and 2 g) some- 

 what vaulted, and a little before its posterior margin produced into a small, acute process directed 

 backwards. - Thoracic legs partly mutilated; judging from the second joint of first pair of legs these 

 are at most a little thicker than second pair; the six posterior pairs (fig. 2 d) are rather slender, and 

 the outer angle of fourth joint has a short seta. 



Abdomen (figs. 2 e and 2 g) a little longer than broad, with the end rounded but yet subangular, 

 and most of the margins regularly convex. Operculum considerably longer than broad, subpentagonal, 

 as the basal margin is long and very moderately convex, the lateral margins feebly convex and distally 

 suddenly curved much inwards, the posterior part of the plate produced backwards, with the tip forming 

 an angle of about 100, and each half of the posterior margin a little concave. - - Uropods (fig. 2 g) 

 somewhat long; the peduncle very broad, the endopod rather robust and about twice as long as the 

 slender exopod. 



Length of the specimen 1.5 mm. 



Remarks. N. spinicornis is abundantly distinguished from all species described on the pre- 

 ceding pages by the antennulse, the very long anterior margin of the front area and the shape of the 

 operculum; besides, the strong telescoping of the anterior segments is very characteristic. The differ- 

 ences between N. spinicornis and the following species are pointed out below. 



