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



the apex, wliicli is narrowly truncate and armed with two small denticles. Excepting 

 these apical denticles, the telson is quite unarmed, and only provided with a few very 

 minute hair-like bristles at the edges. 



The uropoda were partly broken in the specimen examined. They seem to have 

 been comparatively small, the scape not nearly attaining the length of the telson. 



Habitat. — The above described specimen, as also the broken example mentioned 

 above, was taken in the North Atlantic from a very considerable depth. 



Station 79, July 11, 1873 ; lat. 36° 21' N., long. 23° 31' W.; depth, 2025 fathoms ; 

 bottom, Globigerina ooze ; bottom temperature, 35°'9. 



12. Diastylis mystacma, n. sp. (PL X. figs. 1-3). 



Specific Characters. — $ . Anterior division of body greatly swollen. Carapace 

 exceedingly large and deep, with the dorsal surface boldly vaulted in the middle ; 

 pseudorostral projection of moderate length, bordered on each side by an elevated and 

 strongly dentate crest, continued along the anterior part of the carapace as a slightly 

 flexuous serrate keel ; inferior edges of carapace densely serrate in the anterior half; 

 surface finely scabrous from very small microscopic spikes. No distinct eye. Anterior 

 edge of the two first exjaosed segments of trunk minutely denticulate ; penultimate 

 segment with two longitudinal serrate keels dorsally. Epimeral plates of the anterior 

 segments finely serrate at the edges. Last segment of trunk and the three anterior 

 caudal segments each with a pair of small dorsal denticles. First pair of legs of 

 moderate length, terminal joint nearly as long as the preceding. The three posterior 

 pairs of legs very slender, with meral and carpal joints about equal in size. Telson with 

 terminal part as long as basal, slightly tapering and armed with but one pair of lateral 

 denticles. Uropoda comparatively small, inner branch shorter than outer, and composed 

 of two articulations only. Length, 10 mm. 



Remarks. — This very distinct species seems to be most nearly related to Diastylis 

 insignis, described by the author from the Swedish Atlantic Ex^^edition, though easily dis- 

 tinguished by the peculiar dentate crest on each side of the anterior j^art of the carapace, as 

 also by the want of the strong lateral projections occurring on the carapace of that species. 

 Description. — The sole specimen contained in the collection is an adult female with 

 fully developed marsupial pouch. It measures about 10 mm. in length. 



The general form of the body (see PL X. figs. 1, 2) is rather similar to that of 

 Diastylis insignis, the anterior division being greatly swollen and very sharply marked 

 off from the slender tail. 



The carapace is exceedingly large and deep, about twice as long as the exposed part 

 of the trunk, with the dorsal surface boldly arched in the middle, and declining rather 

 abruptly posteriorly, and more gradually anteriorly. The pseudorostral projection is of 



