122 BROOKLYN MUSEUM SCIENCE BULLETIN 3. 3. 
The angulation of th^ posterior tibiae of the males is more plainly 
seen from an internal view and is often very indistinct in small specimens. 
Metallic blue or green specimens are apparently very rare, I have 
seen only one specimen of each color, collected by Mr. C. A. Frost. 
This rather aberrant species can scarcely be compared with any 
North American Donacia. In some way the males are not unlike the 
females of the Siberian Donacia (Sominella) macrocnemia Fisch. The 
head is very similar as in the latter species which, however, has the 
ocular orbits somewhat distinct. The prothorax is similar but is in 
macrocnemia shorter, with more strongly rounded sides anteriorly, and 
the strigate-rugose sculpture is coarser. The sculpture of elytra consists 
of the same long, coarse, transverse rugae as in harrisi, though denser 
and coarser, but the sutural margin is not distinctly sinuate near apex in 
macrocnemia. The internal angulation and serration of the posterior 
tibiae of the males of harrisi are the same as in the females of macrocnemia 
but stronger in the latter. 
Subgenus Plateumar[S Thomson. 
The species of this subgenus are more alike in general form and 
structure and armature of the posterior femora than the species of the 
subgenus Donacia and the two sexes do not differ as much in form and 
armature of hind femora as certain species of the latter. The head is 
always more or less abruptly narrowed and constricted behind the eyes, 
which latter are always small; the tempora more or less distinct; the 
ocular orbits are absent; the mandibles are generally larger but occa- 
sionally as small as 'in certain species of true Donacias; the elytra are 
generally more convex and parallel and usually rounded at tip and the 
sutural margin is sinuate near apex; the intercoxal process of the meso- 
sternum is always narrow; the femora are generally armed below with 
one tooth in both sexes, though in some species only the females, in 
others both sexes, have unarmed posterior femora. The first ventral 
segment is rather short, about as long as the three following joints 
together. 
In nearly all the species the pubescent space near the anterior coxae, 
always present in the species of the subgenus Donacia, is here absent 
with the exception of diversa, which has a small, more or less distinct, 
pubescent space. The vaginal plates are apparently of a more hardy 
texture and the upper plate is generally shorter than the lower, which 
latter is usually triangularly narrowed apically and more or less acutely 
pointed at apex, the sides anteriorly more or less serrate and are ap- 
