SYSTEMATIC ACCOUNT ,8i 



jointed palp, the fourth joint of which bears a slightly raised longitudinal region surmounted by a row 

 of very minute rounded projections ; the endite is indented and bears two simple setae. 



The first, second and last pereiopods are shown in Text-fig. i^e,k and /, as well as the setae on the 

 distal three joints of the first pereiopod. Each pereiopod bears, on the margins of the distal half, 

 a series of small rounded tooth-like projections. 



The modifications of the first and second pleopods of the male and the form of the penis are very 

 similar to those described and figured by Hale (1946, p. 169 and fig. 4, p. 170) for A. tribulis. The 

 penis (Text-fig. 186) is single but distally cleft. The basipodite of the first pleopod (Text-fig. \%a) is 

 about twice as long as broad and has a pronounced curve inwards towards the middle of its outer 

 margin; it bears seven coupling setae on its inner margin (five in A. tribulis) and ten very small teeth 

 on its outer margin (these are also present in A. tribulis). The form of the exopodite is also very 

 similar in the two species, the oblique furrow terminates in a narrow projection, which is bent 



k 



Text-fig. 17. Arcturides acuminatus sp.n. (a) Maxillula (left), x 25. {b) Tip of uropod. (c) Dorsal view of pleotelson. 

 ((i) Maxilla (right), x 15. (e) First pereiopod, x 20. (/) Maxilliped (left), x 25. (^) Lateral view of female, x 7. (/;) Antenna, 

 X 12. (7) Antennule, x 18. (/:) Second pereiopod, x 20. (/) Seventh pereiopod, x 20. 



outwards and is about a third of the length of the broader part of the exopodite. In ^. acuminatus, 

 the distal end of the projection is obliquely truncated to form a pointed extremity (Text-fig. i8«); 

 the appendix masculina of the second pleopod (Text-fig. iSc) is about the same length as the endo- 

 podite, its distal end is flattened and terminates in a curved pointed projection. The exopodite and 

 endopodite of the uropod (Text-fig. 176) are of approximately equal size and each is tipped with a 

 single seta. 



A. acuminatus bears a close resemblance to the genotype A. cornutus Studer and also to a species, 

 A. tribulis, described and figured by Hale in 1946, but differs from them in the following points: 



(i) The narrow distal extremity of the pleotelson tapers to a point in acuminatus whereas in the 

 other two species it is truncate and notched. 



(2) In acuminatus the body armature has body spines less well-developed than those of tribiilus, and 

 the blunt, downwardly directed tooth is not present on the antero-lateral angle of the head. 



(3) In acuminatus the areas above the insertions of the coxal joints are raised. 



(4) The endite of the maxilliped is also diff^erent. 



Both Studer's and Hale's specimens were obtained from Kerguelen Island, and Hale suggested 

 that in view of their great similarity tribulis might be a variety of cornutus. Beddard's material of 



