ISOPODA. 21 



joints of the peduncle of the first antennae. The dilatation of these joints is used as 

 a character also by Schiodte and Meinert. Sars, however, employs the qualified 

 statement, " the first two peduncular joints more or less expanded," and, in fact, 

 describes the antennae as very slender both in Mga arctica, Lutken, and JEga 

 ventrosa, M. Sars. The absence of any expansion from the two peduncular joints in 

 question is conspicuous in the figures given by Schiodte and Meinert of their species 

 AUga nodosa. They further speak of the frontal lamina, that is, the plate above the 

 upper lip between the bases of the second antennae, as large or very large in Mga, 

 but minute or evanescent in Rocinela. But, taking all the species of the two genera 

 together, this distinction does not seem to be stable. 



In the species about to be described the peduncular joints of the first antennae are 

 not specially dilated and the frontal lamina is not very large. But while in these 

 respects it makes an approach to Rocinela, it is clearly separated from that genus by 

 the flagellum of the first antenna? and by the maxillipeds. Its peculiarities tempted 

 me to make it the type of a new genus, but I am content to leave it for the present 

 as a very distinct unit among the many species of the genus /Ega. 



JEga, ommatophylax, n. sp. Plates IV., V. (A), 



The very marked and at present seemingly unique feature of this species pertains 

 to the first peraeon segment of the male. The anterior border of this segment 

 projects a sub-median pair of cylindrical processes over the large contiguous eyes. 

 The specific name has been chosen to suggest that their function is protective to the 

 organs of vision. In Rocinela cornuta, Richardson, the antero-lateral angles of the 

 first peraeon segment are extended straight forwards, probably with the same object. 

 The defence obtained is presumably worth the interference with sight that must 

 result from it. 



Male. The head projects a distally widened round-ended frontal process slightly 

 upturned, with the exception of this process having its dorsal surface almost 

 completely and its ventral surface partially covered by the dark eyes. The first 

 peraeon segment, without iucluding its slightly convergent antero-dorsal processes, is 

 longer than any of the other segments, these varying little among themselves in 

 length or breadth. The first five segments of the pleon are but little narrower than 

 the peraeon and are subequal one to the other, somewhat wider than the telsonic 

 segment, which is broader than long, with its broadly rounded apical margin serrate, 

 carrying spines and setae and having the central point a little produced. 



The eyes meet in the middle line of the head, leaving a little triangular interval 

 above, but occupying all the hind margin. 



The frontal lamina is not large. The bases of the first antennae are concealed from 

 above by the front of the head, and have a slender peduncle with flagellum thirteen- 

 to fourteen-jointed. In the second pair the joints of the slender peduncle increase in 

 length from the second to the fifth, and the flagellum is thirty-two-jointed. 



