178 Trans. Acad. Sci. of St. Louis. 
sixth having a large, evenly and almost semicircularly rounded 
sinus, occupying virtually the entire apex and between two 
and three times as wide as deep, with its contour unmodified. 
Tetramedon n. gen. 
The labrum in this genus is remarkably similar to that of 
Polymedon, but in every other respect the two genera are 
altogether unlike, besides inhabiting quite different faunal 
provinces. The gular sutures in Tetramedon are moderately 
separated anteriorly, converging gradually to the base of the 
head, where they are very narrowly separated and are well 
impressed throughout. The single species known thus far is 
the following : — 
Rather stout, parallel, somewhat depressed, moderately shining, black or 
piceous-black, the elytra bright rufous, except a large basal cloud near 
the scutellum, which is piceous, the legs and antennae pale red-brown; 
head well developed, wider than long, the sides parallel and broadly 
arcuate, the angles broadly rounded, the punctures not very coarse but 
deep and very close-set, mingled with larger circular punctures bearing 
stiffer setae; eyes at somewhat more than twice their own length from 
the base; antennae rather long and thick, subequal in length to the head 
and prothorax together; prothorax oblong, as long as wide, less than 
four-fifths as wide as the head aud punctured like the latter but more 
finely and feebly, the sides straight and subparallel or just visibly con- 
vergent from apex to base, the angles obtuse and distinctly, though not 
very broadly rounded; elytra large, parallel, with slightly arcuate sides 
and well marked basal angles, which are widely exposed at base, dis- 
tinctly longer than wide, slightly wider than the head, two-fifths wider 
and about one-half longer than the prothorax, moderately strongly and 
closely punctured; abdomen about as wide as the head, parallel, the 
sides just visibly arcuate, densely punctulate. Length 4.0 mm.; width 
0.8mm. New York (Hudson Valley)........-+...-..--rufipenne n. sp. 
The unique type of this interesting species is a female, but 
the male secondary characters are probably of the usual sim- 
ple form. 
Platymedon Csy. 
This genus was proposed by the writer some years ago to 
include a peculiar myrmecophilous Paederid of moderate size, 
somewhat depressed and of broadly parallel form, with char- 
