GERAUS. 261 
denticulate on their inner edge. Centrinus, therefore, will have to be restricted to the 
few South-American forms (all of large size *) possessing this structure, and the name 
Gereus, Pasc. (type Centrinus senilis, Boh.), applied to the very large number of 
species having the mandibles straight on their inner edge and more or less pointed at 
the tip f. Odontocorynus is here retained as distinct, as well as Nicentrus, Centrinites, 
and Centrinopus, though these latter are scarcely separable from Gereus. About 100 
species from within our limits are referred to Gerwus, the head-quarters of the genus 
being apparently in Mexico. ‘The male-characters are here of the utmost importance 
in discriminating many closely allied forms, and some of them have scarcely been 
noticed hitherto, such as the greater development of the anterior tibial claw in certain 
cases, the ciliation of the anterior or posterior tibie, or of the under surface of 
the femora, the dilated anterior tarsi, the toothed or notched anterior tibiz, the 
dilated posterior tibie, &c. The prosternal spines vary in development (as in 
Diastethus), and they may be sometimes reduced in the same species to conical 
tubercles. In a few forms the antennal club is elongated in the male, and in one 
(G. serratispinis) the rostrum is sagittiform in this sex. 
The various species may be grouped thus f :— 
a. Rostrum long, slender, strongly arcuate, and of equal thickness throughout ; 
femora sulcate beneath. [Sf unknown.]. . ..... . . . . « Species 1. 
b. Rostrum (except in G. puncticollis) usually more or less thickened towards 
the base; femora (except at the apex) not sulcate beneath. 
a’. Upper surface finely pilose and with patches of white scales at the base of 
the elytra. [gd unknown.] . . 2... 6 ee we ee es Species 2. 
6’. Upper surface not finely pilose, with or without scales or decumbent setz. 
a’. Prosternum (¢) bispinose or bituberculate immediately in front of the 
anterior cox. 
a’. Prosternal spines (¢) very long and serrate; rostrum sagittiform . Species 3. 
b°. Prosternal spines ( ¢) very long, abruptly dilated at the base . . . Species 4. 
c®. Prosternal spines (¢) not or gradually thickened towards the base, 
sometimes reduced to two tubercles. 
a’. Anterior tibie (¢) armed with a triangular tooth on the inner 
edge. 2 6 6 ew we ee we ww we we ee ew + Species 5, 
b*. Anterior tibiz (¢) without tooth on the inner edge. 
a’. Posterior tibize (¢) dilated externally . . . . . . . ~ ~~ Species 6. 
b°. Posterior tibie (¢) not dilated externally. . . . . . « ~ Species 7-53. 
* (O, bicuspis and olfersi, Germ., and C. distinctus, germart, curvirostris, parallelus, westwoodi, Boh. 
+ O, strobeli, Steinh., from “Salvador” must be an Argentine insect. 
+ Amongst those of which the 9 only is known, G. biplagiatus, teniatus, flagellifer, octomaculutus, triplaris, 
coarctatus, duplaris, x-notatum, bifurcatus, omilteme, varius, varipes, and leucomelas may prove to be wrongly 
placed when the ¢ is found. 
