ENTOMOSTRACA OK TIIK SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 301 



The male does not differ nuK-.li from the female, except in the structure of the 

 antennules and of the fifth pair of thoracic legs. The antennules are so modified that 

 they form effective grasping organs. In the fifth pair of legs, the joints are nearly 

 of equal length and their armature is also slightly different (fig. 25). 



Habitat. -Scotia Bay, South Orkneys, obtained in siftings from dredged material 

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



1't'innrks. This species appears to hold an intermediate place between Alteuthct 

 and Pelt idi win. It resembles the first in its general appearance, and also to some 

 extent in the structure of several of its appendages. On the other hand, the structure 

 of the first pair of thoracic legs is somewhat similar to that of the same pair of legs in 

 Peltidium. 



Fain. PORCELLIDIIIX-E. 



Uenus Porcellidium, Glaus, 1800. 



P<>m-llidium ctffinc, Quidor. (PI. IV. figs. 5-13.) 



1906, Porcelli'lium njjini*, (Quidor, Exped. Antarct. Franfaise, 1903-1905, " Copepodes," p. 4, pi. i. figs. 1-19. 



Female. - - The female of this species has a general resemblance to that of 

 Porcellidium ravaniv, Thompson & Scott, described in Supplementary Report VII. 

 of the Report on the Ceylon Pearl-Oyster Fisheries, by Professor HERDMAN. It 

 differs, however, in the form of the first abdominal segment, as well as in the 

 structure of the antennules ; it is also somewhat larger than that species, being about 

 1 mm. in length. 



The antennules are composed of seven unequal joints ; the first three are large, 

 their combined lengths being equal to about two-thirds of the entire length of the 

 antennule. The remaining joints are small, but the fourth and sixth are rather longer 

 than the others (fig. 7). The antenna (fig. 8) has the outer ramus articulated to the 

 end of the first joint of the inner one, and is composed of a single moderately long 

 joint. The mouth appendages and swimming feet are similar to those in Porcellidium 

 raraiuv. The first pair of swimming feet are short, and the first joint of the inner 

 ramus is a broad angular plate widest near the proximal end, but becoming narrower 

 distally ; the end joint, which is very small, is provided with two stout claw-like 

 spines of tolerable length, which usually extend outwardly at about a right angle to 

 the leg ; in the outer ramus the first joint is moderately expanded, but the second and 

 third are smaller. The spinifonn seta' on the outer margin are all dilated at the base 

 and plumose, but the two at the end arc tolerably long and slender. A stout seta 

 also springs from the inner distal angle of the second joint. The claw-like spines on 

 the end joint of the inner ramus are each furnished on the lower edge with a fringe of 

 close-set delicate filaments (fig. 9). 



The next three pairs have both rami three -join ted, and moderately elongated and 

 slender. 



(ROY. soc. EDIN. TKANS., VOL. xi.vm., .VI7.) 



