when the right valve has been removed, and in figs 2—4 some 

 few detail-figures are reproduced on a somewhat larger scale. 



The two pairs of antennae (see fig. 1), as compared with the 

 same organs in Cyprinotus, appear a little more robust, and the 

 swimming setae are appreciably shorter. This is more especially 

 the case with those of the lower antenna?, which do not at all 

 exceed the tip of the terminal claws, whereas in Cyprinotus 

 they reach at a considerable distance beyond the latter. The 

 claws themselves are, moreover, comparatively shorter and thicker 

 and not so coarsely denticulate as in that form. 



The 1st pair of maxillae, though being constructed upon 

 the very same type as in Cyprinotus, slightly differ by the 

 form of the palp and the masticatory lobes (fig. 2). All these 

 parts are on the whole rather more slender, and especially are 

 the masticatory lobes distinguished by their unusually narrow 

 and elongate form. 



Also the two pairs of legs (see fig. 1) would seem to he 

 more slender in form, and the terminal claw of the 1st pair 

 does not show any distinct denticulation. 



The caudal rami (see fig. 1) are rather large and powerful 

 as also distinguished by their peculiar armature. On closer 

 examination the two rami are found to be very unequal in form, 

 the right (fig. 3) being constantly much broader than the left 

 (fig. 4) and nearly of uniform width throughout. This ramus, 

 moreower, exhibits along the outer part of the dorsal edge a 

 dense row of denticles arranged in a pretty regular pectinate 

 manner and successively diminishing somewhat in size upwards. 

 The left ramus (fig. 4) is much narrower, slightly tapering, and 

 has only a few very small denticles of usual appearance close 

 to the upper claws. In both rami the claws are rather unequal 

 in size, the apical being about twice as long as the other, 

 though not attaining half the length of the ramus; both claws 

 are coarsely denticulate along the concave edge, the denticles 

 being sharply defined from the edge, which is not the case with 

 the teeth of the dorsal edge of the right ramus. In f ont of 

 the apical claws a very slender seta, nearly attaining the length 



