754 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



curves rapidly; all the veins are very straight, especially those of the 

 upper half of the wing ; the auxiliary vein terminates in the middle of 

 the costal border, the first longitudinal at the extremity of the straight 

 part of the costa, beyond the middle of the outer half of the wing, the 

 third at the tip of the wing, and the second midway between the first 

 and third ; the third is united to the fourth by a straight cross-vein in 

 the middle of the wing, directly beneath the tip of the auxiliary vein, 

 and about its own length beyond the extremity of the long second basal 

 cell ; the extremity of the third basal cell is very oblique and reaches 

 the tip of the lower branch of the fifth longitudinal vein ; the marginal 

 vein, uniting the third and fourth veins, strikes the former just before 

 the tip, while rhat uniting the fourth and fifth, toward which the fourth 

 bends to receive it, is removed further from the margin by about half 

 the width of the first posterior cell. The legs are slender, scantily 

 clothed with short, fine hairs. The abdomen is broad, oblong ovate, 

 fully as broad as the thorax, broadly rounded at the apex, no longer 

 than the rest of the body, of a light color, with darker incisures, and 

 scantily covered with delicate hairs ; it is composed of five segments, of 

 which the second, third, and fourth are of equal length, the first shorter 

 and suddenly contracted, the apical minute. 



Length of body 7'"'^; diameter of head l.SS"^"!; length of thorax 2.5"»"i; 

 breadth of same 2"^™ ; length of abdomen S.S'""^ ; breadth of same 2.2'^^'" ; 

 length of wing 6.4™"^; breadth of same 1.8™™; length of hind femora 

 1.25°^°^, of hind tibisB 1.251"°^, of hind tarsi 1.25'^°i. 



Cheilosia sp. — Two specimens (Nos. 4113, 4150) of a smaller species 

 of Syrpliidw, preserving the bodies, agree so completely with the last- 

 mentioned species, excepting in their much smaller size, that they are 

 referred to the same genus; but as the wings are almost entirely lost, 

 the reference is only made to indicate the approximate place of the spe- 

 cies, which need not be described until better material is at hand. The 

 length of the body is 4.25"^'". 



Syrplms sp. — A fourth species of this family, and second only to the 

 Milesia in size, is represented by two specimens, reverse and obverse 

 (Nos. 4110,4132), which are too imperfect for description, only the body 

 being preserved ; the form and size of this agree best with the genus 

 Sijrphus. The length of the body is lO™'". 



MYOPID^. 



Poliomyia {~oXiu<;, p.u~ia), nov. gen. 



This genus of Myopidw, most nearly allied to Myopa, appears in the 

 neuratiou of the wings to resemble closely some genera of SyrpMdce, 

 especially Xylota and Milesia, but it altogether lacks the spurious longi- 

 tudinal vein, and the third, fourth, and fifth longitudinal veins are not 

 united at their extremities by marginal veins; indeed, they run, with- 

 out swerving, and subparallel to one another, to the margin. In this 



