754 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



amiaed ; auxiliary vein terminating on the costa beyond the end of the 

 basal third, the first longitudinal vein in the middle of the outer half^ 

 the second longitudinal vein is unusually curved downward at the tip, 

 so as almost to reach the apex of the wing ; the united third and fourth 

 longitudinal veins part from the second very near the base of the wing 

 or within the small tranverse vein ; they divide near the center of the 

 wing and the fifth and sixth longitudinal as near the base as the third 

 and fourth ; the sixth longitudinal vein is straight, and appears to reach 

 the margin of the wing. 



The genus resembles Boletina more than any of the genera figured by 

 Wiunertz, but differs strikingly from it in the approximation to the 

 base of the forking of the third and fourth, and of the fifth and sixth 

 longitudinal veins. In this particular, it closely resembles the Sciarince, 

 but differs from them still more in the length of the auxiliary and first 

 longitudinal veins, and in that the former reaches the costa. The costal 

 rein does not appear to pass beyond the tip of the second longitudinal 

 vein, but this point is obscure. I have dedicated their genus to the dis- 

 tinguished dipterologist Baron Osten Sacken, to whom I am indebted 

 for many suggestions in the determination of these fossils. 



Saclcenia arcuata. — This species is represented by a single female speci- 

 men, more than usually well preserved. The body is pale testaceous, 

 the wings wholly hyaline, but the veins faint testaceous; the antennae 

 are a little longer than the head and thorax together, very slender, of 

 the color of the thorax; the basal joints are subglobular, slightly 

 broader than long, the remainder twice as long as broad, and beyond 

 the middle of the antennse slightly moniliform. In the wings, the base 

 of the hinder cell, using Winnertz's terminology, lies within the base of 

 the upper discal cell, both being nearer the base of the wing than the 

 middle transverse vein, while the base of the middle discal cell is far 

 outside of either of these, near the centre of the wing. The costal vein 

 appears to terminate where the cubital reaches the margin, and the 

 axillary vein nearly or quite reaches the border. The legs are partly 

 detached, and the basal portion of the front pair obscure, but, apparentlj^, 

 the front tarsi are about three times as long as the front tibiae. Length 

 of body 5.65'""; antennae 2'""'; wings 4.25"™; hind femora 3""™; hind 

 tibiae 2™"; hind tarsi 2.4""" ; fore tarsi 2"™. Chagrin Valley. 



A second specimen of the same species is similarly preserved, but 

 wants the wings. The legs, however, are better preserved, and show a 

 pair of apical spurs to the tibiae. The antennae are imperfect, but the 

 proboscis is seen. The length of the curved body is a little more than 

 5.5™'". The legs are detached and confused, so that it is impossible to 

 separate the middle and hind legs; one leg (a front leg, to judge from 

 its length) has the following measurements: femur 1.2"""; tibia 1.4"""; 

 tarsi 1.7'"'" ; another (probably a hind leg) : femur 2.1(?)'""'; tibia 2.25'"'" ; 

 tarsi 1.75""" ; another (probably the opposite of the same) : tibia 2.25""" ; 

 tarsi 1.75""". Apparently, all the tarsi are broken. The tibial spines, 



