HEMIPTERA— HOMOPTEKA— PSYLLlDiB. 275 



2. Pterostigma nigrum. 



Only the body, somewhat distorted, and one fore wing are preserved, 

 which do not permit so complete a description as of the preceding species. 

 The wing appears to be about three times as long as broad, and with the 

 same symmetrical form seen in the preceding species. The postcostal vein 

 is thick and straight, blending into the considerably thickened stigma. 

 The oblique veins are each very gently arcuate with the opening toward 

 the stigma, unusually oblique and little divergent, the general course of 

 the first being scarcely more than forty-five degrees with the postcostal, 

 that of the second not above forty degrees ; the second is more sinuous and 

 terminates fully as far out as opposite the base of the stigmatic vein, the 

 first opposite the base of the cubital, so that the cell is at least four times 

 as wide on the hind margin as at the base. The cubital vein is very faint, 

 especially toward the base, but arises four or five times as far from the 

 second oblique as the latter from the first oblique vein, and scarcely less 

 than half-way from the first oblique to the stigmatic vein ; it has an exceed- 

 ingly longitudinal course and forks very narrowly far before the base of 

 the stigmatic vein, but just how far the single specimen does not permit 

 deciding. The stigmatic vein parts rather rapidly from the stigma and is 

 strongly arcuate at base, but the form of the stigmatic cell can not be made 

 out. The body is very black and uniform throughout, the abdomen short 

 ovate, and well rounded, with no sign of cauda or cornicles. 



Length of body, 3.5™°^ ; of wings, 5""". 



Florissant. One specimen. No. G090. 



Family PSYLLID^E Latreille. 



This little family of leaf fleas, closely allied to the Aphides, but always 

 winged at maturity and showing some curious resemblances in neuration to 

 the Psocidse among Neuroptera, seems to be best represented, like the 

 Aphides, in temperate regions. Hitherto it has not been found fossil, but 

 the shales of Florissant have now yielded remains of two species belonging 

 to two diff"erent groups and representing extinct genera allied to Psylla, 

 Pachypsylla, and Psyllopsis. 



Table of the genera of PsyUida. 



Stem of the cubital veiu before its fork as loiigasthe stem of the subcostal veiu 1. Necropsylla. 



Stem of the cubital veiu beforeits fork distinctly shorter than that of the subcostal vein. .2. Catopaylla. 



