1888.] AUSTRALIAN CLADOCERA. 9 



throughout their whole length, with numerous slender and mov- 

 able setae, three of which on each valve, affixed to the infero- 

 posteal corners, are excessively elongate and generally spread in 

 a radiating manner (see fig. 2). On the inferior edges the setae 

 are more or less inflexed, whereas on the posterior edges they 

 point backwards, and on the anterior flaps outwards. 



As to the sculpture of the shell, nothing more could be de- 

 tected, save a faint punrtatiuii. apparently caused by the nu- 

 merous transverse pillars connecting the two lamellae of the 

 valves and defining the complicated network of canals within 

 the substance of the valves, through which the blood circulates. 



The so-called shell-gland, located between the lamellae of 

 either valve, is of very peculiar appearance and wholly unlike 

 that met with in any other known form of Cladocera. It is (see 

 fig. 1) very large and, instead of forming a simple convolute of 

 canals, it, is divided into three widely diverging branches, the 

 posterior of which is by far the largest. The inferior branch, 

 properly answering to that commonly found in other Cladocera, 

 crosses the anterior part of the valves and terminates at some 

 distance from the inferior edge; the posterior, on the other hand, 

 runs straight backwards along the sides, close to the line con- 

 necting the valves with the upper part of the carapace, and 

 reaches even beyond the middle of their length. Finally, the 

 superior branch is the shortest of the three and passes upwards, 

 almost opposite to the inferior branch. From the point, where 

 the three branches meet, a very delicate and somewhat curved 

 string passes anteriorly to the oral region, its mode of termi- 

 nating being however very difficult to observe. Of the branches, 

 the upper and lower consist each of a double convolute of clair ca- 

 bals, whereas the posterior would seem to contain three such canals. 



The eye, as in Laiona, is located somewhat dorsally, within 

 the obtusely rounded extremity of the head. It is comparatively 

 of smaller size than in that form, but of quite a similar struc- 

 ture, exhibiting numerous refracting crystalline lenses imbedded 

 "» a brownish-red pigment. Owing to its great distance from 

 the optic ganglion, the optic nerves are of quite unusual length, 



