82 DISCOVERY REPORTS 



Boreomysis acuminata sp.n. 



Occurrence: < Fi S- X 4 A - D ) 



St. 2055. 28. iv. 37 (day). East of St Helena, 2000-1400 m., 2 badly damaged juv. 



St. 2064. 3. v. 37 (day). Just south of equator, north-north-east of Ascension I., 1600-1050 m., 2 adult ?9> 



15-16 mm. 

 St. 2065. 4. v. 37 (day). North of equator and south of Sierra Leone, 1600-1400 m., 1 badly damaged adult $. 



(Note on label, 'orange pink'.) 

 St. 2066. 5. v. 37 (day). South-west of Sierra Leone, 1950-1550 m., 1 adult d, 18-2 mm., 1 adult +, 19 mm. Types. 



Description. General form slender and very transparent. Carapace produced anteriorly into 

 a narrow, very sharply pointed rostrum extending in the female to the middle of the second segment 

 of the antennular peduncle. In the male it is shorter and extends only very slightly beyond the anterior 

 margin of the eyes (Fig. 14A-C). Antennules showing marked sexual dimorphism — in the male the 

 peduncle is almost twice as stout as in females of the same size and the flagella are more robust. The 

 base of the outer flagellum in the female is expanded on its inner side and armed with a number of very 

 long, finely plumose setae, but in the male there is little expansion in this region and the setae are 

 comparatively short. The hirsute lobe is long and slender and densely setose (Fig. 14A-C). Antennal 

 scale slightly more than 3! times as long as its greatest breadth; tooth terminating the unarmed outer 

 margin extending well beyond the small apex. Antennal peduncle more robust in the male than in the 

 female (Fig. 14A-C). Eyes very peculiar and characteristic in both sexes. Eyestalk expanded distally 

 especially on its inner side, forming a large triangular projection which terminates in a small rounded 

 papilla. The eyestalk is so transparent that a ganglion at the base of the papilla and the nerves running 

 from it and from the cornea are clearly visible. The cornea is small and is confined to a small area on 

 the distal outer area of the eyestalk — its proximal margin is straight giving it a semicircular shape 

 in lateral view (Fig. 14A-C). Thoracic endopods rather slender; the distal segments of the second 

 pair do not form a sub-chela. Exopods of both second and third pairs of pleopods in the male 

 modified. Uropods slender, only slightly longer than the telson; unarmed portion of the outer 

 margin of the exopod nearly one-fourth of the total length and terminated by two small spines; 

 endopod very slender, distally curving slightly inward; inner margin armed with one delicate spine 

 just distal to the small statocyst (Fig. 14 D). Telson three times as long as the breadth at the base; 

 lateral margins converging gradually towards the apex and very slightly concave; armed with 35-37 

 short, somewhat robust spines which are almost regular, but which in some places show a tendency 

 to seriation. Cleft deep and narrow; nearly one-third of the telson in depth; lateral margins straight 

 for the greater part of their length, but very convex at the distal end so that the apical lobes are evenly 

 rounded; armed with about twenty-six unusually long fine teeth on each side (Fig. 14 D). 



Length of adult male, 18-2 mm.; of adult females, 17-19 mm. 



Colour. In the tube from station 2064 there is a note, ' deep orange ', and in that from station 2065, 

 ' orange pink '. 



Remarks. This species can at once be recognized by the very sharply pointed rostrum and by the 

 peculiar eyes. I was in some doubt as to whether these specimens should be referred to B.fragilis 

 Hansen, because the material is not in good condition and I thought that the form of the eye might be 

 due to distortion. Hansen's description is not very detailed and he only gives two figures. Accordingly, 

 I asked Dr Waldo L. Schmitt whether it might be possible to have the types examined. This was very 

 kindly done by Dr Fenner A. Chace, Jr., who further lent me a few specimens which had been identi- 

 fied as B. fragilis by Hansen himself. From his report on the male holotype and from my own examina- 

 tion of the other material, it was clear that the Discovery specimens did not belong to B. fragilis. 



