ENTOMOSTRACA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 313 



two at the apex ; the apical setse are slender, but the others are tolerably stout. Caudal 

 rami short. 



Habitat. Scotia Bay, South Orkneys; collected in June 1903; Station 325, 

 60 43' 42" S., 44 38' 33" W. 



Genus Pseudothalestris, G. S. Brady, 1883. 

 Pseudothalestris intermedia, new species. (PI. IX. figs. 1-4 ; PI. XII. figs. 27-29.) 



Female. The female of this species is small, measuring only about 0'4 mm. 

 (about g*o of an inch), and has a general likeness to Pseudothalestris pygm&a, Scott. 



The antennules are composed of seven joints ; the second joint is tolerably large, 

 but the next three are each shorter than the one that precedes it ; the two end joints 

 are small, and together are only about equal to the third, as shown in the formula, 

 which gives approximately the proportional lengths of the various joints : 



Numbers of the joints 1234567 

 Proportional lengths 7873234 



In the first pair of thoracic legs, the two-jointed outer ramus is tolerably short, and 

 the seta on the inner margin of the first joint of the inner ramus springs from slightly 

 below the middle of the joint, instead of from near the proximal end. 



The fifth pair of thoracic legs are small ; the basal joint is moderately broad, and 

 the produced inner portion is of a triangular form, and furnished with three setas on the 

 lower half of the inner margin, and with two on the outer margin near the apex : a 

 distinct space also separates these two from the others ; the second joint is small, and 

 bears three setse on the outer margin, one on the inner margin, and one at the apex 

 these setse are all tolerably elongated, as shown in the drawing (fig. 5, PL XII.). 



Male. In the second pair of thoracic legs of the male, the second joint of the 

 inner ramus is provided with five setse two on the inner margin, one near the proximal 

 end of the outer margin, and two at the apex ; and the innermost of the two apical 

 setse forms a stout and claw-like appendage, but the other four Betas mentioned are 

 tolerably slender (see figs. 3 and 3A, PI. IX.). 



Fifth pair small ; the inner portion of the basal joint moderately produced, and 

 furnished with a short, stout seta on the inner margin, and with two at the apex, the 

 outer being considerably smaller than the other (see fig. 4, PI. IX.). 



Habitat. Scotia Bay, South Orkneys; collected in June 1903; Station 325, 

 60 43' 42" S., 44 38' 33" W. 



Remarks. The species described above differs from Pseudothalestris pygmsea, 

 Scott, and Westivoodia minuta, Glaus (both of which it resembles to some extent), in 

 the structure of the female antennules, in the armature of the inner ramus of the second 

 pair of thoracic legs in the male, and in the form of the male and female fifth pair. 

 There are also one or two other points of difference, but those referred to appear to be 

 the most important. 



(ROY. soo. EDIN. TRANS., VOL. XLVIII., 559.) 



