64 CRUSTACEA MALACOSTRACA. III. 



39. Haplomesus tenuispinis n. sp. 

 (PI. V, figs. 4 a- 4 f). 



Immature Female. The material consists of a specimen which has lost the three posterior 

 thoracic segments and abdomen, and of another evidently younger specimen without head and the two 

 anterior segments. After some hesitation I considered these two badly mutilated specimens as belonging 

 to the same species, especially because they show considerable similarity in the shape of fourth seg- 

 ment and its processes. 



Antennulse (figs. 4 a and 4b) somewhat long, reaching the front end of fourth segment; second 

 joint half as long again as the four distal joints combined; third joint only a little longer and thicker 

 than second joint of the flagellum, which is longer than first joint. -- Antennae long and somewhat 

 slender; third peduncular joint rather slender, and only half as long as second joint of the antennulse; 

 fifth joint about two and a half times as long as the third, feebly increasing in thickness from base 

 to end; sixth joint a little longer and distinctly more slender than the fifth; flagellum a little less 

 than twice as long as sixth peduncular joint, i6-jointed. 



The thorax has a pair of moderately long processes on first segment (fig. 4 a) and a pair of 

 distinctly longer processes on fourth segment. The processes on first segment are not quite half as long 

 as the breadth of the segment, very slender, conical, slightly curved, acute, directed somewhat forwards, 

 much outwards and feebly upwards. The processes on fourth segment are in the largest specimen 

 (fig. 4 a) conspicuously longer, but not thicker, than first pair, directed horizontally a little outwards 

 and very much forwards, reaching somewhat in advance of the front margin of third segment; in the 

 small specimen (fig. 4 d) they are proportionately more slender and longer, reaching the front margin 

 of second segment Fifth segment in the small specimen -- about eight times as long as broad 

 somewhat before the middle; while its terminal leg-bearing part is unusually feebly widened, being 

 much narrower than third segment. 



First pair of thoracic legs (fig. 4 c) in the main as in H. quadrispinosus, but fifth joint has only 

 one very long, slender spine and one rather short spine, and sixth joint has a single moderately long 

 spine. The other legs in the main as in H. quadrispinosus, but the distance between the ends of 

 second joints of fourth and fifth pairs, when directed respectively backwards and forwards, is a little 

 longer than in that species. 



The abdomen (figs. 4 e and 4 f) differs much from that in any other species of the genus, 

 excepting to a certain degree H. modestus. In the three preceding species it is divided by a distinct 

 lateral constriction into a moderately short proximal part answering, of course, to the first segment in 

 hchnomesus, and a large distal part, but in H. tenuispinis the proximal part is not only elongate and 

 rather little shorter than the distal part, but is even divided by a distinct constriction (fig. 4 e) into 

 two portions, the anterior somewhat narrower and shorter than the posterior and besides, just in front 

 of the transverse impression between them, armed with a pair of small, spiniform, sublateral processes 

 (d) directed mainly backwards. The constrictions and dorsal transverse impressions show that the ab- 

 domen consists of two proportionately long anterior segments and the large posterior segment, all 

 completely fused with each other and with the three posterior thoracic segments. The posterior seg- 

 ment is somewhat longer than broad and broadest behind, with the lateral margins somewhat feebly 



