RHIANUS,—RHIANINUS. 243 
prominent, flat, widened posteriorly ; elytra triangular, much wider than the prothorax, incompletely 
striate ; pygidium not visible; prosternum unarmed, sulcate, the sulcus extending backward between 
the cox, which are separated by about one-half their own width; femora sublinear, unarmed ; tibie 
angulate at their outer apical angle; tarsal claws free; body broad, convex, rhomboidal, polished, 
glabrous above. 
Type, 2. mexicanus, Pase. 
This genus was based by Pascoe upon an insect he supposed to be the Centrinus 
mexicanus of Boheman, but one of the characters given by him for Rhianus, “ femora 
mutic,” shows that he had wrongly identified the species, and this has been confirmed 
by a comparison of the types. The present insect has the general facies of a 
Diorymerus, and there are no other Central-American forms known to me that can be 
placed with it. The scutellum is unusually large and prominent. 
1. Rhianus mexicanus, (Tab. XIII. figg. 31, 31a.) 
Centrinus (Rhianus) mexicanus, Pasc. Ann. & Mag. Nat. Hist. (6) iv. p. 8323* (nec Boh.). 
Shining, black, the antenne and the apical joint of the tarsi obscure ferruginous; glabrous above, the 
punctures of the median portion of the under surface and of the legs each bearing a hair-like scale, the 
lower surface of the femora and the inner edge of the tibie finely ciliate. Head transversely depressed 
between the eyes; rostrum a little longer than the head and prothorax, stout, thickened at the base, 
punctured to the tip, the antenne inserted far behind the middle, the club long, stout, and acuminate, 
as long as joints 2-7 of the funiculus united. Prothorax moderately convex, the sides arcuately 
converging from the base to the narrow tubulate anterior portion, the base subfoveate on each side of 
the median lobe; the surface with very minute widely scattered punctures. Scutellum smooth, bare. 
Elytra with the striz almost obsolete on the outer part of the disc from a little below the base, the three 
inner ones sharply defined, becoming much deeper anteriorly, the interstices smooth. Beneath somewhat 
closely punctate down the middle, the punctuation becoming much sparser towards the sides, the fifth 
ventral segment slightly depressed aiong the centre. 
Length 6, breadth 4 millim. (¢?) 
Hab. Mexico (coll. Pascoe, in Mus. Brit.). 
One specimen. Very like Centrinus mexicanus, Boh., here referred to Diastethus, 
but with a longer scutellum, sublinear, unarmed femora, and free tarsal claws. The 
locality requires confirmation. 
RHIANINUS, gen. nov. 
Rostrum strongly arcuate, stout ; mandibles straight on their inner edge, not decussate; antennal club ovate ; 
eyes ascending, narrowly separated above; prothorax tubulate in front; scutellum transverse, free, 
densely squamose ; elytra much wider than the prothorax, triangular, deeply striate, depressed along the 
suture; pygidium not visible ; prosternum unarmed, narrowly sulcate; anterior coxe separated by about 
one-third of their own width; femora linear, unarmed; tarsal claws free ; body rhomboidal, polished, 
glabrous above, the scutellum excepted. 
Type, BR. niverscutum. 
The type of this genus is very like Rhianus mexicanus, Pasc., but cannot be 
satisfactorily treated as congeneric with it; &. carinirostris is a diminutive allied 
form. 
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