724 On Aquatic Carnworous Coleoptera or Dytiscide. 
large almost triangular area, they do not quite reach to the lateral margin but 
leave a narrow elongate space there smooth: the epipleure behind the 
shoulders are broad and flattened and obliquely perpendicular. 
The species varies a good deal in size and somewhat in the colour of the legs, 
and often the epipleurze and metathoracic episterna are more or less rufescent : and 
occasionally there may be seen in the male as well as in the female, the rudiments 
of a second claw on the hind tarsus ; this claw is of short broad triangular form, 
and is placed at the extremity of the inner terminal point of the unguicular cleft ; 
in the female of C. binotatus this rudimentary claw appears as a slender elongate 
process placed along the inner margin of the unguicular cleft. 
Aubé has described as occurring in Senegal a species closely allied to C. owas, 
and has called it ©. bimaculatus; the characters he gives to distinguish the two 
are quite without importance. 
I have a female specimen from Doueé’s collection, said to be from Algeria, and 
this differs in no respect from large elongate individuals found in Madagascar. I 
have also a male individual from Lake Nyassa, which is of decidedly more elongate 
form than any specimen I have seen from Madagascar, and the patch of sexual 
pubescence on the intermediate tarsus is only one-half the width of what it is in 
the Madagascar examples. I consider it, however, only a variety of C. owas. In 
the Munich Catalogue, Harold has proposed the name of Trogus caffer for the 
Cybister binotatus of Boh. (nec. Klug), but it is doubtful whether Boheman’s de- 
scription indicates more than a female variety of this species. 
Madagascar. 1065. 
1136. Cybister immarginatus, Aube.—Gravidus, ovalis, latus, convexus, supra 
nigro-olivaceus, prothoracis lateribus omnino vage et obsolete rufescentibus, subtus 
niger, pedibus anterioribus et intermediis piceis femoribus basi apiceque, tibiisque 
anterioribus seepius dilutioribus, pedibus posterioribus nigricantibus ; antennis rufis, 
Long. 37, lat. 21 m.m. 
The male of this species has the front tarsi rather small, attaining only 2?—3 
m.m. in the transverse direction, the pubescent area is correspondingly small, and 
the basal fringing hairs are short so as to project but little beyond the basal 
pubescence. The intermediate tarsi have a rather large patch of moderately short 
pubescence, the patch is narrowly oval in form, its basal termination being 
particularly narrow ; their claws differ but little from those of the female. The 
female has no trace of any sexual sculpture, and there is never the least rudiment 
of a supplementary claw to the hind tarsi. 
The species varies a good deal in size and in colour, it is sometimes nearly entirely 
black; at other times the metathoracic episterna are very rufescent, and other parts of 
the undersurface also become more or less rufescent ; the largest specimens attain the 
