38 DIPTERA OF NORTH AMERICA. [PART III. 



3. Arista feathery ; femora unarmed ; scutellum moderately 

 convex, with six bristles ; type ; P. nigronotata Lw. 



4. Arista feathery ; front femora spinous ; scutellum but little 

 convex, with four bristles ; type : P. pectoralis Lw. 



As in the remaining parts of the organization there is a great 

 deal of agreement among all the Platystomse, and as at the same 

 time the number of the described species is not large enough to 

 require a further subdivision of the genus, we may leave it undi- 

 vided for the present. Walker's genus Valonia is closely allied 

 to Platystoma. Unfortunately, I possess only a single male of 

 Valonia complicata Walk., which, moreover, is not very well 

 preserved. The structure of the head, the thorax, and the feet, 

 as well as the venation, do not show anything which would 

 justify a generic separation from Platystoma. The facts that the 

 second longitudinal vein is a little shorter, and more curved for- 

 ward, and that the small crossvein is a little nearer the end of 

 the discal cell, are evidently not sufficient for such a course. 

 The very much swollen and apparently only too bristly scutellum, 

 as well as the moderate breadth and smooth surface of the upper 

 abdominal segments, would furnish a better ground for a separa- 

 tion from Platystoma. At all events, thus much is evident, that 

 Valonia does not show any distinctive characters more important 

 than those of the four genera would be in which, as I have 

 shown above, Platystoma might be subdivided. 



Platystoma cincta, from Port Jackson, described by Guerin 

 ( Voyage de la Coquille), may be considered as the type of a 

 separate genus, allied to Platystoma. Several Australian and 

 African species are closely connected with it. If I remember 

 right, such species are designated in the Berlin Museum by the 

 new generic name of Pachycephala. But as a genus Pachyce- 

 phalia exists already, I propose the name Scholastes. Such 

 species differ from Platystoma in the head being larger, the front 

 much broader, the portion of the face between the foveas much 

 more excavated, and the much narrower clypeus not protruding; 

 the occiput likewise is much less swollen, so that the head is 

 much more closely applied to the thorax, and appears entirely 

 sessile in the profile ; the thorax is much broader and flatter ; 

 the scutellum likewise, much larger and flatter, but with six 

 bristles ; the tegulse are as much developed as in Platystoma. The 

 structure of the abdomen and of the feet, as well as the venation, 



