1S88.] AUSTRALIAN CLADOCEKA. 37 



the two last pair of legs, are very conspicuous in the living 

 animal from their rythmical swinging movements, constituting as 

 they do the chief organs for effecting the renewal of the water 

 inside the valves. 



The tail (fig. 4) is enormously developed and very mobile, 

 having the form of a rather broad oblong lamella, slightly ta- 

 pering towards the tip, to which the very long and slender cau- 

 dal claws are affixed. The dorsal edge of the tail exhibits 

 above the middle a distinct sinus, indicating the place where 

 the anal orifice is located. The outer part of the edge below 

 this sinus is armed with a double series of rather small den- 

 ticles, about 16 in each row, and moreover at some distance 

 from the edge, on each side, occurs a lateral series of about 8 

 much larger slender spines, the upmost invariably removed from 

 the rest by a rather large interval. These lateral rows of spines 

 do not however reach to the above mentioned sinus. Above the 

 latter the dorsal edge is somewhat curved, strongly compressed 

 and furnished with a single median series of 7 or 8 rather 

 large denticles. Moreover, between the tip of the tail and the 

 lateral series of spines, 4 small denticles occur on either side, 

 and at the base of the caudal claws are affixed 2 extremely thin, 

 almost hair-like secondary spines. The caudal setae, originating 

 from a small knob-like projection where the dorsal edge of the 

 tail terminates, are rather elongate, nearly attaining the length 

 of the tail, and are distinctly biarticulate, with the outer joint 

 beset with scattered cilia. 



At some distance above the tail, the dorsal part of the body 

 juts out as a rather elongate conical process, finely hairy along 

 the posterior edge (see fig. 1). This process generally meets the 

 fold extending within the dorsal edge of the carapace, thus clos- 

 in g up the incubatory cavity posteriorly. 



The intestinal tube is quite simple, without any circum- 

 volutions. Its anterior part, contained within the head, is but 

 very slightly dilated, whereas the posterior part exhibits, previ- 

 ous to joining the short muscular rectum, a considerable saccular 

 dilatation (see fig. 4). 



