EXOPEOSOPA. 79 



quarta tertiae conjuncta ad apicem.") As I have never seen this species (and neither 

 did Eondani), I cannot decide upon this genus. 



Thus of the three genera introduced by Eondani, I adopt only one, and give it a 

 closer definition— Hyperalonia, with four submarginal cells and toothless ungues; in 

 other respects like Exoprosopa. 



I call genuine Exoprosopw those species which have three submarginal cells ; the 

 third antennal joint in the shape of an elongate cone, with a more or less long style, 

 separated from the cone by a distinct suture, and ending in a microscopic bristle; a 

 tooth at the base of the ungues, which, in the majority of cases, is large and distinct; 

 and no pulvilli. This definition, as we shall presently see, excludes from the genus 

 Exoprosopa, as understood by previous authors, certain species that have three sub- 

 marginal cells, but are nevertheless much nearer related to Anthrax than to real 

 Exoprosopce. 



Eyperalonia and Exoprosopa have in common the strong posterior legs, contrasting 

 with the small front pair; the latter are remarkable for their smoothness and the 

 absence of the stronger bristles and spinules which occur on the other pairs, especially 

 on the tibiae. The structure of the front tarsi is peculiar — gradually tapering and beset 

 on both sides with numerous short, delicate hairs; the articulations are indistinct; the 

 ungues small. 



If Eyperalonia is closely related to Exoprosopa, so that both genera might, not 

 unnaturally, remain united as subdivisions of the same genus, there are two other 

 groups of American Exoprosopce, in Macquart's sense, which have very little in common 

 with that genus besides the artificial character of the presence of a third submarginal 

 cell. These species differ from the true Exoprosopa?— 1, in the shape of the antenna?, 

 the third joint being short, onion-shaped, with a very long style, not bisected by a 

 suture (differing in this from the style of Argyrameeba) : 2, in the absence of a tooth 

 at the base of the ungues : 3, in the more delicate structure of the legs ; the difference 

 in size and structure between the front pair and the posterior ones is much less 

 marked ; the front legs less smooth than in Exoprosopa, and beset with bristles or 

 spinules, besides the microscopic pubescence ; the front tarsi do not show the peculiar 

 structure of those of Exoprosopa, their joints are more distinctly marked, and their 

 ungues comparatively larger: 4, in the general appearance, the species are smaller 

 than the genuine Exoprosopa;, their colouring is different, the cross-bands, spots, &c, 

 common among the latter, are wanting here. 



With these characters in common, the two groups just alluded to differ from each 

 other as follows: — 



1. Very long proboscis and narrow lips; no pulvilli. 



2. Short and retractile proboscis, with fleshy lips ; distinct, although small, pulvilli. 

 1. The first of these subdivisions reproduces some of the characters of the South- 

 African genus Litorhynchus as given by Macquart, Dipt. Ex. ii. 1, p. 72 (long proboscis 



