except that the antenna? are shorter, the second joint more dilated, as 

 Say describes it, and the abdomen less dilated distally. The abdomen 

 in my specimens in drying became compressed, and it is possible that 

 the same condition existed in the type, and was too widely restored in 

 drawing. 



The genus approches Triptotricha^ rather closely, but the size, slen- 

 derness, and the presence of but one spur on the front tibiae are all dif- 

 ferent. The presence of but four posterior cells is undoubtedly a nor- 

 mal character, and I doubt that it is at all variable; yet this hitherto im- 

 portant family character will not serve for aught else than for a distin- 

 guishment in the present case; the genus finds its proper location with 

 Triptotricha in the sub-family Psammorycterinae*. Triptotricha, as Loew 

 years ago pointed out, frequently varies in having the third posterior 

 vein abbreviated, and in the examination of a considerable series of 

 T fasciventrh Loew, I have observed the last posterior vein rarely aris- 

 ing from near the base of the discal cell. It is thus possible, that, as an 

 anomaly, a neuration similar to, if not identical with, that of the present 

 species may exist in species of Triptotricha, For this reason I am un- 

 willing to describe the first-mentioned species from the White Mountains 

 until additional specimens shall have assured me that its neuration is a 

 normal feature. In both of these species, however, the single spur 

 on the front tibia will serve, I believe as a generic distinction 

 should such a case possibly occur in Triptotricha where the third poster- 

 ior vein is wholly obliterated and the last vein does not spring from the 

 second basal cell. In the three species of Triptotricha known to me. all 

 the tibiae have two spurs. The formulae for the tibial spurs in this fam- 

 ily, so far I have observed them, may be expressed as follows: 



Agnotomyia, i, 2, 2. Atherix, o, 2, 2. 



Triptotricha, 2, 2, 2. Symphoro?nyia, o, 2, 1. 



Leptis, o, 2, 2. Arihroccras, o, 2, 1. 



Chrysopila, o, 2, 1. 



Arthroceras n. <j. 



In size, shape and general appearance much resembling certain species of Chrysu- 

 ptlo, e. g. C. quadrata. Head in front view much like that of this species, but 

 the front somewhat narrower and the lower part of the face does not form 

 a hemispherical convexity as in the species of Chrysopila, but is in the female 

 nearly straight or gently convex in profile, transversly convex and separated 

 from the sides by two convergent deep grooves more like it is in species of Sym- 

 phoromyia. In the male the grooves are deeper, broader, and more broadly V-shaped 



*Better Vertnilionina:, as, according to the usage of good Zoologists, the genus 

 Psammorycter Blanch, should not replace I'ermilio Macq. because the latter was 

 raised from specific to generic use. There is quite as much propriety in changing 

 Musca vermilio Deg. into Vermilio .Decern as many of the numerous arbitrary changes 

 that have been made in the generic names of diptera. Nor indeed would there be- 

 more impropriety in calling the species Vermilio vermilio Deg. than to call a man Mr. 

 Thomas Thomas. 



