8o DISCOVERY REPORTS 



second spine distal to the first on the inner margin of the endopod ; it may be that this character is 

 variable (Fig. 12 L). Telson long and relatively slender; longer than the last abdominal somite; 

 lateral margins convex, narrowest portion of telson slightly proximal to the base of the cleft ; armed with 

 a large number of spines arranged in a series as in B. rostrata. The large spines of the series are 

 particularly long and slender. Cleft less than one-seventh of the telson in depth with a marked 

 dilatation at the base (Fig. 12 L). 



Length of adult <$, 22-3 mm., of adult ?, 23 mm. 



Remarks. This beautiful mysid can be recognized at once by its extremely short upturned rostral 

 projection; by its robust form; by the stout, powerful endopods of the second thoracic appendages 

 with their strong sub-chelate termination and the two strong spines between which the dactylus fits 

 down ; by the very short unarmed portion of the outer margin of the exopod of the uropod terminating 

 in two spines and by the long ' waisted ' telson with a dilatation at the base of the cleft. Corresponding 

 parts of B. tattersalli and B. bispinosa are figured on the same scale and a comparison of the second 

 thoracic endopods will show how robust this appendage is in the latter species (Fig. 12). The other 

 thoracic appendages are also relatively longer and stouter than in B. tattersalli. 



Distribution. B. bispinosa is a bathypelagic form and has been taken at four stations in the eastern 

 waters of the South Atlantic. The two adult specimens were taken in closing nets fished at 1350- 

 1250 m. and 1400-700 m. respectively. 



Boreomysis insolita sp.n. 



Occurrence: \ &• 3 i) 



St. WS 979. 7. iii. 50 (night). West of Walvis Bay, South Africa, 100-50 m., 1 adult $, 8-2 mm., 1 imm. ?, 2 small 



juv. ??. 

 St. WS 987. 10. iii. 50 (day). South-west of Walvis Bay. Two hauls: (i) 50-0 m., 1 adult i^mm, 1 imm. <$, 7-6 mm., 

 1 imm. $, 7-3 mm., 1 small juv.; (ii) 250-100 m., 3 adult c?6*. largest 8-2 mm., 3 imm. <J<J, 4 adult $$, largest 

 8-4 mm., 3 imm. ??, 4 juv. Types. 



Description. General form small and very slender. Carapace somewhat inflated anterior to the 

 cervical sulcus ; very short in front with the anterior margin evenly rounded and uptilted to form a deli- 

 cate, transparent, almost vertical rim and leaving the eyes completely uncovered; no trace of any 

 rostral angle or projection; antero-lateral angles small and not produced (Fig. 13A-C). Antennular 

 peduncle relatively robust ; second and third segments turned outward from the plane of the first. 

 In lateral view the dorsal margin of the first segment is almost straight and does not display the con- 

 cave contour which is usual in the genus (Fig. 13 A, D). Antennal scale, slender, four times as long as 

 its greatest breadth ; outer margin straight with a very long tooth marking the distal end and extending 

 considerably beyond the truncate apex ; peduncle nearly two-thirds as long as the scale ; composed of 

 four segments, the third of which is set in a different plane from the others giving the peduncle a 

 peculiar distorted appearance. A similar condition is found in some species of the genus Amblyops. 

 Outer distal angle of the sympod produced into a strong sharp spine (Fig. 13 B, E). Eyes relatively 

 large, globular; cornea occupying half the whole organ; ocular papilla small and inconspicuous (Fig. 

 13 A-C). Thoracic appendages small and very slender; second pair with the distal segment of the endo- 

 pod rather swollen and not forming a sub-chela (Fig. 13 F). Second pleopod of the male, exopod nearly 

 twice as long as the endopod and stouter; distal three segments armed with short modified setae 

 (Fig. 13 G). Third pleopod of the male smaller than the second; exopod longer and stouter than the 

 endopod; modified setae at the distal end fewer and longer than in the second pair (Fig. 13 H). 

 Uropods slender ; unarmed portion of outer margin of the exopod one-fourth of the total margin and 

 terminated by two spines, the inner of which is long and nearly twice as long as the outer; endopod 



