SCUDDER ON FOSSIL INSECTS. 753 



globose, a little longer than broad, largest in the luiddle. Wings surpass- 

 ing slightly the abdomen ; the third longitudinal vein originates from 

 the second in the middle of the wing, is very gently arcuate (the con- 

 vexity backward) in its outer half, and appears to terminate just above 

 the tip of the wing ; the fourth longitudinal vein is united by an oblique 

 cross-vein to the third very near the origin of the latter, and the spuri- 

 ous longitudinal vein cannot be made out, from poor preservation ; the 

 marginal vein between these two appears to be very simple, the fourth 

 longitudinal vein bending downward at its tip to meet it. ' The abdomen 

 is as broad as the thorax, fully as long as the rest of the bodj^, broad- 

 ovate, tapering slightly at the base and rapidly beyond the middle, 

 broadest at the second segment ; the first segment is longest, and half 

 as long as broad, the second and third slightly shorter, the fourth still 

 shorter, and the fifth minute ; the abdomen is light-colored, probably 

 yellow in life, and the first three segments are rather narrowly margined 

 posteriorly with black ; the first segment is also similarly margined in 

 front, and besides has a median black stripe of similar width, which 

 divides the segments into equal lateral quadrate halves, — whence the 

 specific name ; the whole abdomen is rather profusely covered with very 

 brief, black, microscopic hairs, which are thickest in the black bands 

 bordering the segments, and next the hind edge of the fourth and fifth 

 segments, producing a dusky posterior margin, similar to but narrower 

 than the dark belts of the preceding segments, and of course very 

 inconspicuous. 



Length of body 18"^°^, of head 2.85""™, of thorax 5.65™"", of abdomen 

 9^5mm . breadth of front 2.4'^'», of head 4.5°^™, of thorax 6™% of abdomen 

 gmm . probable length of wing li-S'"'" ; length of hairs on abdomen 

 0.04"™ . width of dark abdominal bands 0.5™^. 



Cheilosia ampla.— This species is primarily founded on a single speci- 

 men (No. 4112) which Mr. Bowditch and I found in the Richardson 

 shales at Green River, and which preserves nearly all parts of the 

 insect. There is also a specimen with its reverse (Nos. 4135, 4141) 

 which we obtained at the same place, and another (No. 40) which 

 Mr. Richardson sent me from these beds, agreeing with the first- 

 mentioned specimen, but a little larger. As only the bodies are pre- 

 served, they are temporarily placed in this connection, until other 

 material is at hand, while the species is described wholly from the 

 more perfect individual. This has a body more nearly of the shape of 

 an Orthoneura, the abdomen being broader and stouter than is usual 

 in Cheilosia; but the wings are much longer than in the species of 

 OrtJioneura I have seen, and both the shape of the wing and its neura- 

 tion agree well with Cheilosia. The head is round and moderately large, 

 the thorax stout and rounded ovate, the scutellum large, semilunar, 

 twice as broad as long; all these parts are dark brown. The wings 

 are very long and narrow, extending much beyond the tip of , the abdo- 

 men, the costal edge very straight until shortly before the tip, where it 



