AEGYEAMCEBA. 105 



always perfectly hyaline). All the brown spots are somewhat darker and the hyaline space within the 

 basal cell is much smaller, sometimes very small, 

 length 10 millim. ; but much smaller specimens occur. 



Hab. Mexico, Northern Sonora (Morrison). 



I have twelve males and six females. 



Two males in Prof. Bellardi's collection, from Tehuacan, Mexico (Sumichrast), may 

 perhaps belong to this species; they show, however, the cloud in the marginal cell 

 which, in the specimens from Sonora, is peculiar to the female only (see above) ; the 

 brown spot at the origin of the second vein is much larger, fills out the distal end of 

 the second basal cell, and coalesces with the brown on the posterior cross-vein ; there is 

 a cloud in the middle of the anal cell ; no stump on the fork of the third vein. The 

 dusty condition of the specimens renders a further comparison impossible. 



N.B. — Adventitious spots, cross-veins, and stumps are rare ; one male has a brown 

 spot at the end of the stump on the fork of the third vein, and a pale dot on the fourth 

 vein instead of the small cross-vein, &c. 



It is very probable that this species, which seems to be common, has already been 

 described, but from some rubbed specimens : I have not been able to recognize it from 

 the descriptions. As I have a considerable number of well-preserved specimens of both 

 sexes before me, I thought it worth while to give a complete description. 



9. Argyramoeba fur. 



Argyramcebafur, O. Sack. Western Dipt. p. 244. 



Hab. United States, Texas. — Mexico (Sumichrast, coll. Bellardi), Northern Sonora 

 (Morrison). 



A male and a female from Mexico in Prof. Bellardi's collection, and a female from 

 Northern Sonora, belong to this or to a closely allied species. The brown of the wings 

 is paler than in the original specimens from Texas, and encroaches much less upon the 

 two basal cells ; the dusty condition of the body of the Mexican specimens does not allow 

 a closer comparison. The individual from Sonora is cleaner, and answers the description 

 quite well, with the exception of the difference in the extent of the brown on the wings, 

 already noticed. The size of the latter specimen is only 8 to 9 millim. I reproduce 

 the description from the ' Western Diptera ' : — " Face and front pollinose with yellowish- 

 grey, and clothed with short black pile ; on the front, some very minute pale yellow 

 hairs are mixed with the grey ones ; the grey occiput is more or less clothed on the 

 orbits with hair of this latter description. The dull greyish-black ground-colour of the 

 thorax and scutellum is in part covered with a short, yellow, appressed tomentum ; a 

 large tuft of yellowish-white pile between the humerus and the root of the wings, 

 extending to the upper part of the pleurae ; a frill of whitish hairs, mixed with black 

 ones, on the anterior margin of the thorax, opposite the occiput ; the edge of the scu- 



biol. CENTE.-AMEE., Dipt., December 1886. p 



