214 Mr. H.AV. Bates on the Longicorn Coleoptera 



generally tricostate. The elytra are generally trigonal, at times 

 oblong, depressed or slightly convex, their surface sometimes 

 even, but generally furnished with a ridge on each at the base, 

 which often projects forwards, and in many species is prolonged 

 posteriorly to the apex : the latter is generally briefly and ob- 

 liquely truncated, but it is sometimes whole, and at other times 

 largely truncated, with the external angles projecting into a 

 tooth or spine. The pro- and mesosterna are moderately broad, 

 but variable in this respect ; the former never very narrow, the 

 latter not contracted between the haunches nor extremely short, 

 but always of a quadrangular shape. Both are plane on their 

 surface in some species, but they are more generally tumid or 

 tuberculated, ridged on the sides, and projecting : in a number 

 of cases the mesosternum is projecting, whilst the prosternum 

 is simple ; in many species, however, both project and have their 

 opposing faces steeply inclined. They vary greatly in species 

 otherwise closely allied, although they are similarly constructed 

 in all those species which approximate to Steirastoma. The tibia? 

 are, in one section of the genus, strongly dilated and compressed. 

 The terminal ventral segment is sinuate-truncate in the 6 , and 

 entire in the § . 



The flattened shape of the muzzle distinguishes this genus 

 from the preceding. There is no character to separate it from 

 Dryoctenes, Serv. The shape of the sterna distinguishes it from 

 Polyrhaphis. From Steirastoma it differs at once in the simple, 

 conical, lateral thoracic tubercles ; and from Alphas by the pyri- 

 form basal joint of the antennae. I have incorporated with it the 

 genus Pteridotelus, White, — with some hesitation, however, as I 

 think Pteridotelus might probably form a natural group if the 

 generic definition were modified so as to include all those spe- 

 cies which have the terminal joints of the antennas shortened 

 and thickened in any degree, or thickened and ciliated in 

 the 6 . The species on which it is founded (Pteridotelus 

 laticornis) cannot be generically separated from A. pupillatus, 

 Chevrolat, which, again, is closely allied to A. spectabilis, n. sp., 

 and A. pilicornis, Chevr.*, all four most diversified in ornamenta- 

 tion of the antenna?, but agreeing in the thickening in some 

 way or other of the terminal joints. These species have in 

 common also rounded anterior acetabula, slender fore tibia?, and 

 steeply inclined sterna. As a genus, however, it would not be 

 sharply limited from Acanthoderes : other species have the ter- 

 minal antennal joints somewhat shortened and ciliated, without 



* To these may probably be added A. antennatus of Guerin-Meneville 

 (Ins. Recueillis par Osculati, Verb, des Z. B. Verein in Wien, 1855, p. 599). 

 A. pupillatus is from Venezuela, and A. pilicornis from Mexico ; both are 

 \mdescribed. A. spectabilis belongs to the Amazonian fauna. 



