BYRROMORPHUS.—HEXANCHORUS. 127 
narrowed to the front, the sides obliquely straight, the base in the middle strongly 
lobed, the lobe nearly truncate behind. Elytra depressed at the humeral angle. 
Only a single individual, in very fragile condition, has been obtained. 
DISERSUS. 
Corpus elongatum, pube brevissima dense vestitum. Labrum latissimum, latius clypeo; antenne ad basin 
distantes, 11-articulate, articulo basali elongato, secundo simplici, haud transverso, 3°-11™ subsequa- 
libus, intus perparum productis. Coxe anteriores maxime distantes ; prosternum ante coxas brevissimum, 
fere nullum. Coxe intermedi valde distantes ; mesosternum a metasterno sutura profunda disjunctum, 
medio impressione magna prosterni processum recipiente. Pedes elongati, femoribus anterioribus pre- 
sertim elongatis, tibiis compressis. 
The insects for which I propose this name are allied to the European Potamophilus, 
but differ in so many respects that they cannot be placed in the same genus therewith. 
The extreme separation of the front and middle coxe is most remarkable, as is also the 
elongation of the anterior femora; the impression on the mesosternum is broad and 
definite, and becomes narrower behind, in conformity with the shape of the prosternal 
process, whereas in Potamophilus the impression is indefinite and quite narrow in front, 
becoming broader behind and reaching the metasternal suture. 
In addition to Disersus longipennis, the genus will comprise the Colombian Potamo- 
philus goudotui, Guér. | 
1. Disersus longipennis. (Tab. IV. fig. 6.) 
Elongatus, niger, opacus, supra pube concolori brevissima vestitus, subtus pube densissima cinerea; antennarum 
basi testacea ; elytris striatis, apicibus sinuatis et prolongatis. 
Long. 4, lat. 14 lin. 
Hab. Panama, Volcan de Chiriqui 2000 to 3000 feet (Champion). 
Thorax strongly transverse, much narrowed in front in a gentle curve; the base 
much prolonged in the middle, and the prolongation deeply emarginate behind; on 
each side of this basal lobe there is a minute impression; but the rest of the surface 
is even. The remarkably elongate elytra are marked by regular very shallow striae, 
which are very distinctly though not coarsely punctate. 
Only two individuals have been found; in one of them the prolongations at the apex 
of the wing-cases are more slender than in the other. Although this is the only differ- 
ence I perceive, I believe it indicates the sexes, the specimen with slender prolongations 
being the male. 
HEXANCHORUS. 
Corpus suboblongum, capite angustulo, oculis vix prominulis, prothorace elytris angustiore, pube brevissima 
dense vestitum. Antenne distantes, 11-articulate, articulo basali elongato, 2° simplice, 3°-11™ subsimilibus, 
simplicibus, intus subserratis. Pedes elongati, graciles, tibiis intermediis et posterioribus subcompressis. 
Coxe anteriores late distantes; prosternum in processu magno, triangulari productum; coxe intermedia 
perdistantes, mesosternum parum impressum, a metasterno sutura profunda disjunctum. 
