Lamellicorn Beetles. 175 
Sp. 4. Aigidium? Guianense, Westw. (Pl. XII. fig. 5a—5 d.) 
fig.? breve convexum, castaneum, pronoto posticé parum an- 
gustato, mandibulis extus cornu obtuso armatis. 
Long. corp. lin. 43. 
Habitat in Guiana. D. Schomburghk. In Mus. nostr. 
E reliquis differt habitu, lateribus pronoti minus rotundatis, ut 
et structura partium nonnullarum essentialium. Vix tamen genus 
distinctum format. 
Clypeus anticé rotundato-productus, punctatissimus. Labrum 
exsertum, semicirculare, ciliatum. Mandibule exserte, versus 
medium lateris externi cornu brevi lato truncato armate, 
dentibus duobus, supero bifido ut in A gidiis veris. Maxillee 
etiam ut in illis, Jobo interno vero in hamum simplicem pro- 
ducto. Pronotum transversum, marginibus serrulatis, et cum 
elytris fere continuis; in medio versus marginem anticum 
parum longitudinaliter impressus et punctatus, spatio postico 
lzevi nitido et fere punctis destituto, lateribus vero puncta- 
tis. Elytra punctata; punctis in strias fere regulares (10 in 
singulo) dispositis. Tibiee anticze acute 3-dentate, unguibus 
simplicibus. Tarsi 4 postici articulo basali intus ciliis rectis 
numerosis instructo. 
Oreunus, Macleay. 
(Pl. XII. fig. 9, and details.) 
This is an interesting genus, which evidently forms a connecting 
link with such of the smaller Dynastid@ as have the head cornuted, 
and the thorax excavated in front in the males. The entire struc- 
ture of the mouth, however, proves its nearer relationship with the 
preceding genera; and hence the opinion of Latreille (Régne An. 
iv. 549), that it is identical with Oryctes, cannot be adopted. 
The description of the trophi given by Mr. MacLeay disagrees 
so completely with the numerous dissections which I have made 
of nearly every species, that it is necessary to give the following 
characters of the parts of the mouth. 
Labrum exsertum, transversum, anticé emarginatum, angulis 
rotundatis, margine antico valde setoso. Mandibule late 
planiuscule, extus valde curvate, intus dentibus 4 acutis 
armate, dente 2do majori, margine interno versus basin 
membrana setosa instructe. Mazille bilobe, lobo exteriori 
obtrigono, angulo interno acuto, dorso longe ciliato, ciliis 
curvatis et spinulosis, lobo interno parvo corneo, setigero, 
