COLEOPTERA. 
465 
All the Byrrhii remain on the ground in sandy localities 
It is impossible to describe the Clavicornes of our second section, 
although a very natural one, but by the reunion of several characters. 
Some of these Insects are removed from all others of the family by 
their antennae, which consist of nine or six joints ; they are those, 
which, in this respect, seem to approximate most closely to the Palpi- 
cornes. The antennae of the other Clavicornes of the same section 
are composed of eleven or ten joints ; but sometimes they are not 
much longer than the head, and from the third joint form an almost 
cylindrical or fusiform club, arcuated and somewhat serrated ; some- 
times they are nearly filiform and as long as the head and thorax 
united ; but here, as in most of the other subgenera of the same divi- 
sion, the tarsi are terminated by a large joint furnished with two 
strong terminal hooks. Those of some — Heterocerus, Georissus — 
consist of but four joints. 
The body of these Insects is generally ovoid, and their head 
plunged to the eyes in a trapezoidal thorax, with a recurved lateral 
margin, and terminating posteriorly in acute angles ; the prsester- 
num is dilated anteriority i', and the legs are imperfectly contractile. 
They are found in the water, under stones in the vicinity of shores, 
and frequently in the mud : some of them — Dryops — are allied to the 
Gyrini by the structure and shortness of their antennae. 
I will divide this section into two tribes The Insects which com- 
pose the first or the Acanthopoda are remarkable for their flattened 
and tolerably wide tibiae, armed anteriorly with spines ; for their 
short quadriarticulated tarsi, the hooks of Avhich are of the usual size; 
and for their depressed body. The preesternum is dilated. The an- 
tennae are a little longer than the head, arcuated, and formed of 
* For the other species, see Fabricius, Olivier, Schoenherr, Gyllenhal, &c. 
The genus Murmidius, Leach, according to that gentleman, belongs to this tribe. 
The antennge are composed of but ten joints, the last of which forms an ovoido-glo- 
bular club. See Lin. Trans., XIII, p. 41. 
i' The Potamophili excepted. 
:j; We might also divide the section in the following manner : — 
I. Antennae composed of eleven joints. 
A. Antennae clavate and very short. 
a. Tibiae spinous ; tarsi quadri-articulated, 
Heterocerus. 
b. Tibiae simple; five joints in the tarsi. 
POTAMOPHILUS. DrYOPS. 
B. Antennae filiform or slightly enlarged near the end, as long as the head 
and thorax. 
Elemis. 
II. Antennae nine or six joints. 
Macronvchus. Georissus. 
VOL, III. 
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