species of Heteromerous Coleoptera. 319 
liar transverse rugze in the middle, and the part thus marked is 
more or less distinctly separated from the other under parts of 
the head by an oblong furrow on each side. Near to these in- 
sects are the Nycteltde, also a South American group, in which 
the throat-plate presents a more striking peculiarity,—that of 
having a distinct and deep mesial groove immediately under the 
mentum, and extended more or less in the longitudinal direction ; 
they however have the labium almost entirely hidden. 
Platesthes silphoides. Piatesth. ater, nitidus, corpore oblongo, late- 
ribus fere parallelis; capite distincte punctatis ; thorace crebre 
punctatis, lateribus piceis ; elytris punctis distinctis adspersis, sin- 
gulo tricostatis; antennis tarsisque piceis.—Long. corp. 6 lin. ; 
lat. 3 lin. 
This insect was found by Mr. Darwin at Port Desire, Patagonia : 
in general aspect it greatly resembles a St/pha. The head has large 
punctures scattered on its upper surface, but on the fold covering 
the base of the antennze and under surface they are smaller, more 
dense, and for the most part confluent. The thorax is very thickly 
punctured, the punctures distinct and of a triangular form; on 
and near the lateral margins, however, they are less numerous 
and more delicate: on the anterior portion of the thorax the la- 
teral margins are scarcely reflected, but they become gradually 
more so towards the posterior margin, where the reflected portion 
is broad; a slightly impressed line runs parallel with, and close 
to the lateral margm. The elytra have the dorsal surface nearly 
flat, but on each elytron are two sharp longitudinal ridges, be- 
sides a third, which forms the lateral keel: between the ridge on 
each elytron which is nearest the suture, the space is flat, but 
the other interspaces are concave, and the whole surface has di- 
stinct, and widely, and irregularly scattered punctures : the ridges 
themselves have a few punctures. The produced apical portion 
of the elytra is pitchy ; distinct scattered punctures are observable 
on all the under parts. 
Scotobius Akidoides. Scot. ater, obscurus ; corpore supra fere plano, 
punctulato ; thoracis marginibus lateralibus reflexis ; elytris carina 
laterali distincta.—Long. corp. 9lin.; lat. 44 lin. 
This species, brought by Mr. Darwin from Port Desire, Pata- 
gonia, is remarkable for the produced and reflected lateral keel 
of the thorax, the distinct lateral keel to the elytra, and the 
absence of any distinct sculpturing on the upper parts of the 
body, to which peculiarities we may add, the very slight convexity 
of the dorsal surface of the thorax and elytra. In size it is nearly 
equal to the Scotobius pilularius ; its thorax, however, is larger in 
proportion to the elytra than in that insect, and the anterior tibise 
are stouter. The head is distinctly punctured; the thorax is 
