848 On Aquatic Carnivorous Coleoptera or Dytiscide. 
and Carabidze are themselves distinct families, and that as its departures from the 
Carabide are in the Dytiscidze direction it may be placed with the latter. It isa 
creature which may be considered to have retained a more primitive condition in 
certain portions of the organization, (antenn:e, maxillary lobe, and legs, coxee excepted). 
than have other members of the Dytiscidze or Carabidee, while its hind coxz and 
thoracic segments have been the subjects of an evolution similar to that of the same 
parts in Dytiscide. It is Dytiscid inasmuch as it lives in water, it is Carabid inas- 
much as it moves on a solid surface in that water ; now as there are no Carabidze 
having the middle coxal cavities formed as they are in Amphizoa and as in this 
respect it agrees with the majority of Dytiscide, these reasons entitle us to place 
it with the latter in a natural classification. 
Note.—I consider that the punctate antennee of Amphizoa may be justly considered 
a more primitive condition of those organs than the pubescent antennee of Carabidee 
or the glabrous antenne of Dytiscidze, for the following reasons; the antennz of 
Carabidze are complex organs of sensation, perfection being obtained by means of - 
punctuation (?), setze, and delicate pubescence,* the simply punctate antenne of 
Amphizoa are therefore clearly more primitive than the punctate-setose-pubescent 
antennz of Carabide. As regards the comparative primitiveness of the glabrous. 
antennz of Dytiscide and the punctate antenne of Amphizoa, the facts are not so 
clear, and it would at first appear that the glabrous antenne of Dytiscidz should be 
treated as more primitive than the punctate Amphizoa antenne; but there is reason 
to believe that the antenne of Dytiscidee have been more or less punctate before 
becoming glabrous; thus in Pelobius (the most imperfect Dytiscid or Carabo- 
Dytiscid), the basal joint of the antennze is a good deal punctured, in Scutopterus 
(S. horni, Crotch) a higher form, a slight punctuation of the basal joint exists, and 
traces of such punctuation may be perceived even in Dytiscus, while in the highest. 
Dytiscidze (Cybister for example) the antenne are completely polished and free from 
punctuation. In writing of these insects I consider therefore I am entitled to treat 
antennz with a punctuation on the basal joints as more primitive than polished, or 
highly pubescent, antenne. 
I. 17.--Genus HYDROVATUS. (Vide p. 321.) 
This aggregate is formed by the union of about forty species. The individuals 
are of small size, and of broad, convex, short, sometimes quite rotund form ; the 
elytra are more or less acuminate behind, and there is frequently a small spine 
projecting from the termination of the body ; the swimming iegs are very slender 
and little developed. The clypeus is large, and overhangs the labrum ; this, how- 
ever, 1s seen to be exserted and visible when the undersurface of the head is. 
* I say this without considering at all what relation this punctuation may bear to the pits described by 
Erichson and others as forming part of the sensitive apparatus of the antennz of the Coleoptera. 
