1871.} 247 
The only metallic-coloured species of the genus at present described. 
In general form, distance of marginal stria from the margin, and number 
of strie, it quite accords with the characters given by Schaum for the 
group, although quite differing in colour. 
Rio Janeiro (Squires). In my own collection and that of Mr. Grut. 
Oxs.—Besides the species above recorded as found in the Amazons 
region, the following may be enumerated as occurring there. P. hir- 
sutus, Schaum; P. clitellaris, Erichs.; and P. jucundus, Schaum. All 
are found on the moist margins of pools, especially when half dried up 
in the hot season, and readily take wing when disturbed. I have taken 
them flying also in the evening. This habit may help to explain the 
wide distribution of some of the species. 
The list of species of Pericompsus in Gemminger and v. Harold’s 
catalogue will have to be modified by the addition, besides the above- 
described, of Bembidium circuliforme (Solier) from Chili, and the with- 
drawal of P. punctatellus of Motschoulsky, which has seven striz 
besides the marginal one. 
Genus Xystosomus, Schaum. 
This genus has not been admitted as distinct from Tachys by Gem- 
minger and y. Harold, although it is much more sharply defined than 
Pericompsus, which they have adopted. The character on which it was 
chiefly founded is the simple apex of the anterior tibie, the apex in 
Tachys being externally dilated and obliquely truncate. The species 
are of very broad, ovate, and sometimes inflated, form. The elytra in 
the two species known to Schaum are perfectly smooth, in those de- 
scribed below, they are more or less distinctly punctate-striate and 
much less convex. 
Xystosomus inflatus, Schaum, Berl. Ent. Zeits., 1860, p. 202, t. ii, f. 9. 
+ turgidus, Schaum, ad. 1868, p. 89, t. iii, f. 8. 
XYSTOSOMUS OVATULUS, h. sp.—X. turgido major, multo minus con- 
venus; elongato-ovatus, nigro-ceneus, fronte bisulcata, thorace transverso, antice 
rotundato-angustato, angulis posticis rectis, supra convexiusculo, linea ab- 
breviata dorsali profunda, basi utrinque fovea magna et extus carina elevata ; 
elytris latis, regulariter ovalibus, supra lineatim subtilissime punctatis, stria 
marginal medio interrupta; antennis, palpis, pedibusque testaceo-rufis, femo- 
ribus tibiisque medio infuscatis. Long. 1 lin. 
The colour is brassy-greenish or blueish-black ; the minute punc- 
