128 PARNIDA. 
The insect for which I propose this genus is allied to Potamophilus, but differs in so 
many points of its structure that I am obliged to isolate it. The head is free, and, 
though the mouth can be much bent inwards, is not retractile ; the labrum is as broad 
as the clypeus, and its membranous or ciliate border quite small; the apical joint of 
the maxillary palpus is so closely connected with the preceding joint that the two appear 
to form only a single large joint. The front coxe are but little elongate externally, 
are placed close to the front of the prosternum, and widely separated. The middle 
coxee are more widely separated than the front ones; and the mesosternum between 
them is marked only with an indefinite depression for the reception of the very broad 
prosternal process. The hind coxe are also very broadly separated. 
The insect is more nearly allied to the European Potamophilus than to Disersus, and 
should be placed between the former genus and Phanocerus. The articulation between 
the prothorax and afterbody appears to admit of greater motion than in the allied 
forms. 
1. Hexanchorus gracilipes. (Tab. IV. fig. 7.) 
Suboblongus, opacus, niger, supra pube fusca, subtus pube brevissima cinereo-micante vestitus, antennarum 
pedumque basibus flavis; prothorace antrorsum angustato, pone apicem transversim constricto, ad 
angulos posticos impresso ; elytris subtiliter striatis, striis ad basin punctatis. 
7 5] 
Long. 14, lat. 2 lin. 
Hab. Mexico, Chinantla (Sal/é). 
This species is very readily identified by the profound depression extending across 
the thorax a little behind the front margin. The lobe formed at the base of the 
thorax in front of the scutellum is very short. No punctuation can be seen on the 
surface of the prothorax. 
The male has the basal ventral segments depressed in the middle, the apical 
segment emarginate at the extremity, and the legs apparently longer than in the 
female ; in the latter sex the apices of the elytra are a little prolonged. 
The species was labelled Potamophilus flavicornis, Chevr., in the Sallé collection, and 
also in an old French collection in my possession; but as that name is not an applicable 
one, I have not used it. The few specimens examined show much variation in the 
sculpture of the elytra and the form of their apices; but I am not able to detect any 
good specific distinctions. 
PHANOCERUS. 
Corpus suboblongum, parum elongatum, pube brevi densissime vestitum. Antenne distantes, 11-articulate, 
articulo basali elongato, secundo simplici, magno, tribus sequentibus minutis, ceteris clavam compactam 
ovalem formantibus. Caput liberum. Coxe anteriores parum distantes, intermedia late distantes. 
Prosternum in processu gracili elongato productum. Pedes sat elongati, tibiis simplicibus haud 
compressis. 
This genus is allied to Potamophilus, but differs from it by the structure of the 
