species of Heteromerous Coleoptera. 319 



liar transverse rugse in the middle, and tlie 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 NyctelidcBj 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. Platesth. 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 Silpha. The head has large 

 punctures scattered on its upper surface, but on the fold covering 

 the base of the antennse and under surface they are snialler, 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 margin. 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 Akido'ides. Scot, ater, obscurus ; corpore supra fere piano, 

 punctulato ; thoracis marginibus lateralibus reflexis ; elytris carina 

 laterali distincta. — Long. corp. 9 lin.; lat. 4^ 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 tibiae 

 are stouter. The head is distinctly punctured; the thorax is 



