i8o DISCOVERY REPORTS 



It has already been pointed out in an earlier report (1933, p. 266) that the shallow-water fauna of 

 these two areas is distinct. Each area has its own representative species; it is interesting therefore, 

 that, of the two known species of Pseudidothea, one should belong to the group found outside, 

 and the other to the group lying inside the Antarctic Convergence. 



Genus Arcturides Studer, 1882 

 The diagnostic characters have been given in the introductory remarks on the family (pp. 173-174). 



Arcturides acuminatus sp.n. (Text-figs. 17, 18) 



Arcturides cornutus Studer, 1882, p. 57; 1884, pp. 15-17, pi. i, fig. 4; Beddard, 1886, p. 108. 



Occurrence. St. 1562: 17. iv. 35, 46° 51-7' S., 37° 56-5' E. to 46° 54-8' S., 37" 53-8' E., 97-104 m., i ^. St. 1564: 

 7. iv. 35, 46° 36-5' S., 38° 02-3' E. (off Prince Edward Island), 110-113 m., i $. 



The male holotype is from St. 1562, the female holotype from St. 1564. 



Description. The male specimen measures 12-5 mm. in length and 2 mm. in greatest breadth, the 

 female 10 mm. in length and 1-5 mm. in greatest breadth; the body is subcylindrical and scarcely 

 depressed (Text-fig. 17^). The head bears a pair of bluntly pointed, forwardly directed dorsal spines; 

 the antero-lateral angle is rounded; the eyes are large and lateral in position. The first pereion somite 

 which is fused with the head is separated from it by a well-marked groove ; it is somewhat deeper than 

 the head and bears a pair of short knob-like dorsal spines and a similar but smaller pair of lateral ones. 



Thepmow somites increase in length from the second to the fourth, the fifth and sixth are subequal 

 and about half the length of the fourth, the seventh is considerably shorter. The second, third and 

 fourth somites each bear two pairs of short dorsal spines similar to those on the first segment; a 

 lateral pair, one on either side, placed in a position midway between the dorsal pairs, is also present; 

 the area just above each coxal joint is raised and bears a very small spine. On each of the last three 

 somites a single pair of small dorsal and a pair of lateral spines are present as well as a small one on 

 each coxal area. 



The abdominal segments are coalesced to form a pleotelson, the shape of which, in dorsal view, may 

 be seen from Text-fig. 17 r; on the dorsal surface within the anterior third of the pleon are two rows 

 of four very small spines ; a number of smaller ones are scattered on the surface behind these rows. 

 Posteriorly the pleotelson is drawn out into a somewhat acute point which extends beyond the 

 extremities of the uropods. 



Each antennule (Text-fig. 17/) extends to about the middle of the third peduncular joint of the 

 antenna; each consists of a peduncle of three joints, the first one of which is very broad, the second is 

 about half the width of the first and the third slightly narrower; the three joints are of approximately 

 equal length; the second joint bears two strong spines on its inner margin. The flagellum consists of 

 a single joint equal in length to the combined length of the two distal joints of the peduncle; it bears 

 three sensory setae and a few simple ones at its distal extremity, and four more sensory setae on the 

 distal half of its margin. 



The antennae (Text-fig. 17A) measure 6-5 mm. in length, each consists of a peduncle of five and 

 a flagellum of three joints. The first segment is very short, the second about twice the length of the 

 first, the third is five times as long as the second, and the fourth and fifth increase in length, the fifth 

 being half as long again as the third. The flagellum is about half the length of the fifth peduncular 

 joint, and its first joint is greater in length than the distal two together. Setae are present on the outer 

 margins of the peduncular joints and scattered on the surface of the joints of the flagellum. 



The mouthparts are of the usual type, the form of the maxillule and of the maxilla may be seen from 

 Text-fig. I'] a and d. The maxilliped, the distal portion of which is seen in Text-fig. 17/, has a five- 



