550 



Ake nordenstam 



The variability within this species has been shown to be very consider- 

 able. In the 6 specimens from Masatierra the females are rnore strongly 

 sculptured than the males. In the females the dorsal tubercles on all the 

 thoracic segments are usually distinct. Only in one female (length 6 mm) 

 were they obscure on the ist thoracic segment. 



In the males only the median pair of tubercles is developed on the ist 

 to 3rd or 5th segment. In the posterior thoracic segments the tubercles are 

 the same as in the female. The carina on the coxal plates is totally absent 

 in the males, so that the 3 posterior coxal plates are slightly visible in dorsal 

 aspect. 



Of the 4 tubercles on the last abdominal segment (cf. Tattersall 1913, 

 PI. XLIX, fig. 5) the minute posterior pair is sometimes totally absent, also 

 in the females. 



Suborder Asellota. 



Fam. Janiridae. 



Genus Jaera Leach 18 13. 



Jaera antarctica Pfeffer 1887, Vanhoffen 1914. — Text fig. 12. 



One small specimen (male), taken together with 

 Tanais lineatus. 



Loc. Juan Fernandez, Masatierra, 30 — 40 m, sand 

 with calcareous algae. 



Distribution: South Georgia, (Pfeffer 1887), 

 Kerguelen (VanhOffen 1914), Falkland Islands (taken 

 by the Swedish antarctic expedition 1901 — 1903 and 

 studied by the author at the Natural History Museum, 

 Stockholm). 



Jaera antarctica Pfeff. differs from the allied 

 species Jaera serrata Barnard in a number of details, 

 e.g. 1st pleopods of male (fig. 12). On these the rami 

 are provided -udth 2 hollows, which probably function 

 as receptacula seminis. 



Fig. 12 

 first pleo 



Jaera 

 pods of 



antarctica, 

 male, X104. 



