306 Dl; THOMAS SCOTT ON THE 



Genus Machairopus, G. S. Brady, 1883. 

 Machairopus austral Is, new species. (PL VI. figs. 20-28.) 



Female. Body depressed, anterior portion considerably expanded. Length about 

 I'l mm. 



Antennules elongated and slender and composed of nine articulations; the second 

 and third joints, which are nearly of equal length, are longer than any of the others ; 

 the fifth and sixth arc also subequal, but very small, while the end joint is narrow and 

 rather longer than the one immediately preceding. Antennae and mouth organs some- 

 what similar to those in Machairopus idyoides, Brady. 



First pair of thoracic legs stout ; outer ramus much shorter than the inner one ; 

 while the first joint of the inner ramus is considerably longer than the second, as shown 

 by the drawing (fig. 25). The next three pairs are slender. 



Fifth pair lamelliform ; proximal joint small ; end joint elongate ovate, widest 

 anteriorly, the greatest width equal to rather more than one-third of the length ; both 

 lateral margins fringed with minute bristles ; this joint is also furnished with three 

 apical setse, the innermost being very short, while the other two are moderately 

 elongated. 



Caudal rami short, about as long as the last abdominal segment. 



Habitat. Scotia Bay, South Orkneys; obtained in sittings from some dredged 

 material collected in April 1903 ; Station 325, 60 43' 42" S., 44 38' 33" W. 



Machairopus major, new species. (PI. IV. figs. 14-24.) 



Female. Resembling the species last described, but larger. Length, 1'5 mm. 



Antennules composed of nine joints ; second and third joints moderately stout, 

 subequal in length and longer than any of the others, the two combined being equal to 

 the entire length of the following six joints ; end joint longer than the preceding one 

 (fig. 15). 



Mandibles elongated and narrow, the masticatory end obliquely truncate ; mandible 

 pulp small and two-branched. First maxillipeds somewhat slender, but the second 

 pair are moderately stout. 



All the four pairs of swimming legs are tolerably stout ; in the first pair, the outer 

 ramus scarcely reaches to the end of the first joint of the inner ramus ; the first and 

 second joints of the inner ramus are nearly of equal length. In the next three pairs, 

 the inner ramus is rather longer than the outer, and the marginal spines of the outer 

 ramus are short and stout. In the fifth pair, the second joint is broadly foliaceous, 

 somewhat ovate in outline and widest near the proximal end, the greatest width being 

 equal to about half the length ; a slender seta springs from a notch near the middle 

 of the outer margin, and there arc also about four slender and moderately elongated 

 setae on the bluntly rounded apex of the joint (fig. 23). 



(ROY. soc. KUIN. TRANS., VOL. XLVIII., 502.) 



