574 GEOLOGICAL SURVEY OF THE TERRITORIES. 



part of the segment somewhat produced, without reachiug the last seg- 

 ment; setsB pale-brown; feet darker brown; wings yellowish hyaline, 

 with a dull-yellow stigma ; veins brown. 



Length, 17-19 millimeters; alar expansion 31-33 millimeters. 



Habitat. — Bridger Basin, Wyoming (Garman) ; Cache Valley, Utah 

 (0. Thomas) ; Colorado Mountains, August (W. L. Carpenter). 



I saw only three females, in a very bad condition, in alcohol. The 

 two species above described are the dwarfs of this genus; the smallest 

 species known, Pt. proteus, having twice the length of Ft. regularis and 

 Ft. hadia. The gills are well visible in the alcoholic specimens of Ft. 

 hadia, 26 pairs in number, to wit, 6 between the head and the pro- 

 thorax ; 6 between the prothorax and mesothorax ; 6 between the meso- 

 thorax and metathorax ; 2 between the posterior feet ; and 6 on the basal 

 segments of the abdomen. The maxillary palpi are longer than the 

 mouth, the basal joint short, the other long, equal, thicker at the tip; 

 the labial palpi are similar. The palpi show a simihir formation as the 

 apical joint in the phryganideous genus Hydropsyche. The external 

 membrane is cut or split in a somewhat spiral manner, so as to give to 

 every joint the appearance of a large number of small joints imper- 

 fectly soldered together. This formation of the pali)i belongs to all the 

 species of Fteronarcys, and is exceptional for this genus only in the 

 whole family of Ferlina. 



These two small species agree in all characters with the larger species, 

 at least so far as the females are concerned, as the males are still un- 

 known. The wings are divided into quadrangular cells, perhaps a little 

 more regular than in the larger species. The venation of Fteronarcys 

 seems to resemble the most the remarkable fossil genus Miamia. 



ACRONEIIRIA. 

 A. dbnormis. 



Perla abnormis, Hagen, Synop., 17, 1. 



This species appears to vary in a very high degree. The late B. 

 Walsh, after repeated observations of living specimens, confirmed varia- 

 tion in size and color, in the reticulation of the wings and in the number 

 of the quadrangular areoles, which are sometimes nearly or altogether 

 wanting; the shape of the prothorax and the vulvar lamina of the 

 female, commonly of a constant shape in this family, offer also slight 

 variations in this species. 



The male has usually long and well-developed wings ; however, two 

 short-winged males now before me seena to belong to this species. The 

 material in my collection of dry and alcoholic specimens, though rich in 

 specimens from different localities, seems to be not yet sufficient to 

 decide the question whether we have here several very closely-related 

 specie* or simply varieties of A. abnormis. 



Two females from South Montana and a male from Snake River, 

 Southeastern Idaho, collected by Prof. C. Thomas, differ as follows: 

 The colors are darker, the abdomen yellow beneath, on each side dark- 

 brown. The male, in worse condition than the females, is a short-winged 

 one ; the shape of the prothorax somewhat different, perhaps only altered 

 by the bad preservation. The vulvar lamina of the two females is more 

 produced than usual, covering one-half of the following segment ; the 

 apical margin is nearly semicircular, notched very little in one female, 

 and not at all in the other. 



A cast nympha-skin from Eagle Eiver, Colorado, August 30, collected 

 by Mr. Carpenter, belongs to a very large species. Length, 33 milli- 

 meters; setse, 26 millimeters. There is nothing known concerning the 



