NO. 5.] ACCOUNT OF THE SPECIES. Ill 



The natatory legs (figs. 912) are built upon the Cyclopoid type, the 

 basal part being very broad and lamellar, and both rami distinctly 3-articulate, 

 and not differing much in size. In each pair the 2 legs are held together 

 by a broad chitinous plate, intercalated between the 1st basal joints, so as 

 only to admit of simultaneous movement (see fig. 9). Although these legs 

 are of essentially the same structure, yet, on a closer comparison, several 

 minor differences may be found to exist between them, making it necessary 

 to describe each pair separately. 



The 1st pair of legs (fig. 9) have the rami somewhat shorter than in the 

 succeeding pairs. On the other hand, the basal part is fully as large, and 

 has the inner corner of the 2nd joint rectangular, with a straight, deflexed 

 spine attached to it. On the outer side of this joint, as in the 3 succeeding 

 pairs, a small bristle is attached. The outer ramus is a little longer and also 

 broader than the inner, and has the terminal joint about the length of the 

 other 2 combined. Each of the latter carries outside a strong spine, but only 

 the 2nd joint has a natatory seta inside, the 1st joint being devoid of any 

 such seta, both in this and the 3 succeeding pairs. The terminal joint has 4 

 natatory setee, and 4 spines gradually increasing in length distally, 3 of them 

 issuing from distinct ledges of the outer edge, the 4th from the tip. All the 

 spines, both in this and the succeeding pairs, are bordered by a hyaline, finely 

 serrated rim. The inner ramus is fringed outside with delicate cilia, and has 

 the terminal joint as long as the other 2 combined. It carries 7 natatory 

 setae, 5 of which belong to the terminal joint, which, moreover, has at the tip 

 a spine of the same structure as those of the outer ramus. 



The 2nd pair of legs (fig. 10), like the 2 succeeding pairs, have the inner 

 corner of the 2nd basal joint produced to a short acute projection, but without 

 any spine. Both rami are more elongated, and of about equal size, the 

 terminal joint in both being considerably longer than the other 2 combined. 

 The number of spines on the outer ramus is the same as in the 1st pair, 

 but the terminal joint has one additional natatory seta. The inner ramus 

 has only 6 such setae, one on the 1st, 2 on the 2nd, and 3 on the last joint. 

 On the other hand, there are 3 spines on the terminal joint, 2 of which issue 

 from the tip, the 3rd from a ledge of the outer edge. 



The 3rd pair of legs (fig. 11) have the rami still more elongated, the 

 outer one differing from that of the 2nd pair in the absence of the proximal 



