Relations of Bunops in the Family Macrothricidce. 337 
close together, and the fornices do not extend to the rostrum. 
This head is evidently derived from a form like that of Acanthole¬ 
beris , which has been flattened into a crest. In Bunops , the 
head seems to have been derived from a form like that of 
Ophryoxus. Its dorsum is not evenly rounded, but bends ab¬ 
ruptly ventrally at a point near that where the fornices meet 
the dorsal edge. The crest is not carried out to the rostrum, but 
the forehead is flattened, even made concave. It is bounded by 
a stiffened edge which can hardly be anything except the fornix, 
although it has not the form characteristic of the fornix in the 
other genera. Above the eye rises a hemispherical elevation 
of the cuticle, which is evidently a portion of the median frontal 
ridge of Ophryoxus , retained to give the eye a better field of 
vision. Thus the relationship of Drepanothrix and Bunops is not 
particularly close, although at first glance such a relationship 
seems probable. It is probable that the former genus is related 
rather to Acantholeberis , while Bunops looks more toward 
Ophryoxus. The crest or keel seems to be an independent de¬ 
velopment in each genus. 
The post-abdomen shows two types in the Macrothricidce , that 
with both post- and pre-anal portions, and that whose pre-anal 
part only is developed. 
POST-ABDOMEN. 
Possessing post-anal part. -{ 
Anus terminal 
Guernella. * 
Grimaldina. 
Bunops. 
Ophryoxus. 
llyocryptus. 
Drepanothrix. 
Lathonura. 
< Streblocerus. 
Acantholeberis. 
Macrothrix. 
Of the three American genera possessing a post-anal projec¬ 
tion of the post-abdomen, Bunops has the smallest and llyo¬ 
cryptus the largest. Streblocerus , whose post-abdomen is most 
like that of Bunops in general form, does not possess this pro- 
* Cladoceres nouveaux du Congo: J. Richard. Extract des Memoires 
de la Societe Zoologique de Prance pour l’annee 1892, pp. 1-10, Figs. 1-6. 
