102 | HYDROPHILIDA. 
acuminate behind, so that it is of a very short and broad rhomboidal form, but in 
certain positions appears triangular, owing to the comparatively slight elongation of 
the middle in front. The central piece of the mesosternum is brought down to the 
plane of the middle of the metasternum, and forms thus, in front of the middle coxe, 
an angular piece with a strong margin on each, exhibiting, in fact, what Mulsant, in 
speaking of Cyclonotum, calls the “ arrow-head form ;” this arrow-head sends backwards 
a piece which is closely connected with the rather broad front edge of the middle of 
the metasternum. The legs are short, with the femora very short and very broad, the 
front femora, indeed, being angular near the base; the tarsi are rather stout, quite 
short and rigid, the divisions between the joints being difficult to perceive; these arti- _ . 
culations are, however, transverse, not oblique; the three basal joints are short, and 
differ little from one-another in length, but the fourth joint is quite as long as the two 
preceding together. Although I cannot see certainly the base of the tarsus, it is 
possible that there may be a short basal joint (as seen in the anterior tarsus of 
Cyclonotum) concealed by the extremity of the tibiz. ‘The under surface of the body 
exhibits a peculiar opacity, such as is seen in Cercyon; the basal ventral plate is carinate 
in the middle. A special peculiarity of the insect is a prominence of the mentum and 
adjoining parts of the under surface of the head, as a consequence of which there occurs, 
just behind the mentum and insertion of the maxille, an abrupt transverse depression | 
extending all across the head. 
The size and form, the short legs, and small rigid tarsi give the insect a great. 
resemblance to Chetarthria, from which genus it is in most other respects very 
different; and there can be no doubt that the place Perochthes should occupy is 
between the Cyclonotum group and the Cercyon group of genera. 
1. Perochthes globulus. (‘I'ab. III. fig. 11.) 
Hemisphericus, piceus, supra nitidus, pedibus rufis; antennis, tarsis palpisque testaceis; capite thoraceque 
impunctatis, nitidis; elytris vix striatis sed seriatim fortiter punctatis, seriebus ante basin desinentibus. 
Long. #-, lat. 3 lin. . 
Hab. Muxico (Sallé), Jalapa (Hoge) ; Guaremana, El Tumbador, 2500 feet (Champion). 
Head without distinct sculpture, clypeal suture obliterated. Mentum with a very 
dense, excessively fine sculpture, rendering it quite opaque, but without pubescence, 
its lateral margins with a few yellow sete. Thorax very closely applied to the elytra 
and accurately continuing their outline; its surface smooth, shining, and impunctate. 
Elytra with rows of very coarse punctures, which, however, do not reach quite to the 
base ; the outer of these rows does not run parallel with the lateral margin, but touching 
it behind diverges much from it in front; interstices impunctate. Legs very short ; 
femora short and extremely broad, the intermediate very. finely but not densely punctate 
beneath, the hinder shining and impunctate. 
