LYSIANASSIDAE 



7i 



Occurrence : 



2. 



3- 



4- 



5- 

 6. 



St. MS 68. South Georgia. 2 <$<$ 7-7-5 mm., 2 $$ 9-10 mm., 1 ovig. $ 13 mm., 



2 juv. 5 mm., from pharynx of Ascidian. 



St. 39. South Georgia. 1 ^8mm.,2 $$ 10 mm., 6 ovig. $$11-13 mm., Z 4J UV - 5-6 mm. 



St. 42. South Georgia. 2 $$ (1 ovig.) 9 mm., 1 juv. 6 mm. 



St. 45. South Georgia. 59 specimens 5-14 mm., a few $<$ and juv. mostly $$ 



incl. some ovig. 



St. 123. South Georgia. 3 <$<$ 7-5-8 mm., 28 $? (1 ovig.) 9-13 mm., 7 juv. 



3-8 mm., from branchial chamber of large Ascidian. 



St. 149. South Georgia. 1 $ 7 mm., 12 $$ 10-12 mm., from branchial chamber 



of Ascidian. 



Fig. 29. Orchomenella macronyx, Chevr. a. Telson. b. Profile of epistome and upper lip. c. Gnathopod 1, 

 with palmar denticles further enlarged, d. Gnathopod 2 (setae omitted), e. Uropod 3 with part of margin 

 further enlarged. 



Remarks. These specimens are evidently the adults of Chevreux's species. As 

 Chilton remarks in the Scotia specimens, the eye is narrower oval than in Chevreux's 

 figure, and in the adult widens slightly below. 



The 4th and 5th side-plates are as figured by Chevreux (fig. 7 D, C). The transverse 

 depression is present on pleon segment 3 , and the profile of segment 4 is quite cha- 

 racteristic. The telson has a narrow slit between the rather broadly rounded lobes, 

 which appear to be quite unarmed. 



The 1 st joint of antenna 1 is very plump and gives a rounded appearance to the front 

 of the head. Epistome slightly convex, but not prominent. 



Gnathopod 1, 6th joint short and stout, palm well developed, transverse, with two 

 small spines at angle and set with a series of little straight processes, some of which are 

 often bifid or fimbriate, with spaces between them. Gnathopod 2, 6th joint oblong, 

 widening distally, minutely chelate, the finger short and stout. 



Peraeopod 3, 2nd joint considerably more expanded than in Chevreux's figure. It 

 is not confined within the 5th side-plate, but can move freely outside. 



Uropod 3, rami broadly lanceolate, both margins of both rami minutely serrulate. 

 This is a most characteristic feature and serves at once to distinguish the species. 



A single accessory branchia on both segments 5 and 6. 



Distribution. Palmer Archipelago; South Orkneys. 



