72 



DISCOVERY REPORTS 



Orchomenella rotundifrons, n.sp. (Figs. 27 c, 30). 



Occurrence: St. 174. South Shetland's. 10 $$ (1 ovig.) 11 mm. 



Description. Head with lateral angle rounded. Eyes large, oval, widening a little 

 below, black. Pleon segment 3 with postero-inferior angle quadrate, the hind margin 

 slightly convex. Pleon segment 4 with the carina gently convex behind the usual de- 

 pression, then upturned into a small triangular tooth, the hind margin of which slopes 

 down obliquely (not vertically as in cavimamis). Telson about twice as long as wide, 

 cleft for two-thirds its length, lobes slightly dehiscent, each with apical spine and three 

 lateral spines. 



Epistome nearly straight, not prominent, upper lip gibbous. 



Antenna 1, 1st joint very stout, when folded down giving the front of the head a 

 rounded appearance as in macronyx. 



cq> 



Fig. 30. Orchomenella rotundifrons, n.sp. a. Profile of epistome and upper lip. b. Proximal joints 

 of peraeopod 3. c. Gnathopod 1. d. Gnathopod 2 (setae omitted), e, Telson. 



Gnathopod 1, 6th joint stout, narrowing distally, palm short, transverse, gently con- 

 vex, entire, defined by one spine; finger short, stout, matching or only slightly over- 

 lapping palm. Gnathopod 2, 6th joint moderately broad, minutely chelate. 



Peraeopod 3, 2nd joint very strongly expanded, subcircular, hind margin slightly 

 serrate. 



Uropod 3, inner ramus not reaching the 2nd joint of outer ramus, inner margins of 

 both with plumose setae, outer margins spinose. 



Remarks. It seems necessary to institute a new species for these specimens, which 

 will not fit into any of the described ones. They might be referred to proximo, Chevr., 

 except that Chevreux does not specially mention the carination on pleon segment 4, 

 comparing his specimens with obtiisa, Sars, where the carina is of quite a different shape. 

 Moreover the postero-inferior angle of pleon segment 3 is distinctly rounded in obtiisa. 



The objections to referring them to nodimamis , Wlkr ., are that the hand of gnathopod 1 

 has no tubercle on the lower margin, and the shape of the carina on pleon segment 4 

 is quite different (see Fig. 27 1). 



