58 THE VOYAGE OF H.M.S. CHALLENGER. 



11. Diastylis erinaceus, n. sp. (PL IX. figs. 9-14). 



Specific Characters. — % . Carapace very large and tumid, surface evenly vaulted, 

 and armed with numerous equal-sized spines ; pseudorostral projection of moderate 

 length; inferior edges of carapace denticulate in the anterior part only. No distinct 

 eye. Exposed part of trunk smooth, not attaining half the length of the carapace. 

 Tail very slender, slightly spinulose, the three anterior segments each provided dorsally 

 with a pair of somewhat stronger spines and four ciliated setse. Antennulse with the 

 basal joint armed with a longitudinal row of spines, outer edge minutely serrate; second 

 joint nearly as long as basal; third much smaller. Antennae somewhat irregularly 

 twisted, with six strong cdiated setae arising from the middle part, and two unciliated, 

 curved setae at the extremity. First pair of legs very elongate, with basal joint strongly 

 spinous, carpal and propodal joints exceedingly elongate and nearly subequal, terminal 

 joint much smaller. Second pair of legs with carpal joint twice as long as the two last 

 joints taken together. Meral joint of the three posterior pairs of legs much longer than 

 carpal. Telson rather elongate, basal part regularly cylindrical and much longer than 

 terminal ; the latter gradually tapering, with two small apical denticles ; lateral edge 

 of telson unarmed. Uropoda comparatively small, with the scape shorter than telson. 

 Length, 13 mm. 



Remarks. — The present species would seem to be very nearly allied to Diastylis 

 josephinas, described by the author, from the Swedish Atlantic Expedition. It differs, 

 however, by the carapace being relatively more tumid, and by its spines being equal-sized, 

 whereas in Diastylis josephinas some of the spines are much longer than the rest. 

 Moreover, the exposed part of the trunk is not spinous as is the case in that species, and 

 the telson, though exhibiting a very similar form, wants the numerous denticles found 

 along the edges of the basal part in Diastylis josephinw. 



Description. — Of this form I have only had an opportunity of examining a single 

 female specimen, and the broken anterior part of another. The length of the perfect 

 specimen is about 13 mm. 



The form of the body (see PI. IX. figs. 9, 10) is that characteristic of the genus, 

 the anterior division being considerably dilated and sharply marked off from the slender 

 tail. 



The carapace is very large and tumid, considerably broader than high, and more 

 than twice as long as the exposed part of the trunk, with the dorsal surface considerably 

 arched and gradually declining both anteriorly and posteriorly. The pseudorostral 

 projection is of moderate length, horizontally projecting, with the upper surface 

 somewhat depressed at the base, and the tip sharply pointed. The inferior edges of 

 the carapace are strongly curved at the middle, and finely denticulate in their anterior 

 part. As seen from above (fig. 10), the greatest breadth of the carapace occurs anterior 



