ENTOMOSTRACA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 547 
The male does not differ much 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° 48’ 42” S., 44° 38’ 33” W. 
Remarks.—This species appears to hold an intermediate place between Alteutha 
and Peltidiwm, 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. 
Fam. PoRCELLIDIIDA. 
Genus Porcellidium, Claus, 1860. 
Porcellidium affine, Quidor. (Pl. IV. figs. 5-13.) 
1906, Porcellidium affinis, Quidor, Expéd. Antarct. Frangaise, 1903-1905, “ Copepodes,” p. 4, pl. i. figs. 1-19. 
Female.— The female of this species has a general resemblance to that of 
Porcellidium ravane, Thompson & Scott, described in Supplementary Report VII. 
of the Report on the Ceylon Pearl-Oyster Fisheries, by Professor Herpman. 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 
ravane. 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 spiniform sete on the outer margin are all dilated at the base 
‘and plumose, but the two at the end are 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-jointed, and moderately elongated and 
slender. | 
