,oo DISCOVERY REPORTS 



appears to be a small median protuberance between the innermost pair of spines and the setae 

 may have been broken off (Fig. i8F, G). 



Length of adult female 21-5 mm. 



Remarks. The length and armature of the telson is so unusual and the apparent division of the eye- 

 plates so pronounced, that at first I felt that it would be necessary to found a new genus for this 

 species. On closer examination it is apparent that the eyes are fused along the posterior portion of their 

 inner margins and are therefore in conformity with the definition of the genus Pseudomma in this 

 respect. The telson is different from that of any other described species of the genus. Its unsual length 

 in proportion to the lengths of the last abdominal somite and the uropods and the arrangement of the 

 lateral spines, in a series of large spines with smaller ones between them, differentiates P. longicaudum 

 from all the known species of the genus. The male specimen shows no modification in the rami or in 

 the setae of the fourth pair of pleopods but, as they are obviously not fully developed, it may be that 

 modifications may appear in older animals. The telson of the adult female is not in good condition and 

 many of the spines arming its lateral margins are missing. Those which are present indicate that there 

 is less difference in size between the large lateral spines and the smaller ones between them than there 

 is in juvenile animals and that the apical spines are relatively much shorter. In the young specimen 

 these spines are very long, measuring nearly one-sixth of the length of the telson, but in the adult 

 female they only measure about one-fourteenth of the length of the telson. 



Distribution. This species was taken at only one station by 'Discovery' — in the Schollaert 

 Channel, Palmer Archipelago, in a net fishing at 160-336 m. 



Pseudomma magellanensis sp.n. 



Occurrence: v &• v 



St. WS 748. 16. ix. 31 (night). Magellan Strait, 30o(-o) m., 1 adult £, 9-25 mm., 1 adult ?, with well-developed 

 empty brood sac, 9-4 mm. Types. 



Description. This species very closely resembles P. sarsi in general appearance. Carapace with 



the anterior margin short and only very slightly convex, leaving the whole of the eyeplate exposed 



(Fig. 19 A). Antennule with the third segment longer than broad and longer than the first and second 



segments together; well-marked rectangular lobe in the middle of the distal margin on the dorsal 



surface between the bases of the flagella. On the outer side of the anterior margin of this process, there 



is a strong spine ; the inner half of this margin is armed with two very small spines and one or two 



setae whose bases are not swollen (Fig. 19A). Antennal scale small, three times as long as broad, 



extending beyond the distal margin of the antennular peduncle for about one-third of its length ; 



apex only very slightly longer than the large tooth which terminates the unarmed outer margin 



(Fig. 1 9 A). Eyeplate large and very long, extending forward to the proximal margin of the second 



segment of the antennular peduncle ; the eyeplate is not evenly convex from side to side, but rises 



along the middle line of each of its halves to a marked ridge. This ridge is so distinct that it might 



almost be regarded as a keel running backward from a small protuberance on the anterior margin and 



curving backward and downward to a shallow trough, which extends backward from the cleft of 



the anterior margin. This trough is so well marked and the cleft so deep, that the rudimentary eyes 



appear to be only contiguous. Close examination, however, reveals that they are of the true Pseudomma 



pattern. Lateral margins armed with 9-10 coarse teeth extending from the antero-lateral angles for 



three-quarters of the length of the lateral margins (Fig. 19A). Thoracic endopods missing. Fourth 



pleopod of the male with the exopod longer than the endopod; composed of eight segments; distal 



segment armed with two very long plumose setae which are slightly modified at their tips; endopod 



