I06 TRANS. ST. LOUIS ACAD. SCIENCE. 



2, full twice as long as wide, h wider behind than before, the humeral an- 

 gles separated by a short space from its base, and respectively J and f of 

 the way from these angles to the tip there is another tooth-like angle, the 

 3 lateral interspaces each gently concave, and the joint widest at the hind- 

 most angle. Joint i is black, with a small, obtrigonate, dorsal, yellowish 

 spot at tip, and there is a large, blackish cloud on each anterior angle of 

 joint 2, the space between and behind these 2 clouds yellowish. The rest 

 of the abdomen pale rufous. 6. The legs are pale rufous, but all the coxae 

 and trochanters are pale yellow. 7. The areolet is triangular and slightly 

 peduncled, its exterior side a little convex, the 2d recurrent vein entering 

 it exactly at its tip. Bullze 4, B, C, D, and E; C and D very wide apart, 

 and E rather nearer to the angle of its vein than to the areolet. Length 

 (^ .24 inch. Front wing c^" -20 inch. 



The ? (as described by Mr. Cresson) differs from the above (f only as 

 follows : — I. There is a dark stain on the middle of the face, and the tips 

 of the antennae are " yellowish," not rufous. 2. There is no j'ellow spot 

 on the disk of the mesonotum, only the tip of the scutel is yellowish, and 

 the metascutellum is immaculate. 3. The posterior tibiae are brownish. 

 4. The abdomen is "short, broad, and subdepressed" ; joint i black im- 

 maculate, and the sides of 2-4 (not of 2 only) blackish. Length 9 (Cres- 

 son) .21 inch. 



One c?. As the differences between my (^ and Mr. Cresson's $ 

 are mostly sexual, or such as may perhaps be ascribed to varia- 

 tion, I have considered the two as provisionally identical. 



Genus CTENISCUS, Haliday (= Exenterus, Hartig). 



Head large and transverse. Clypeus moderate, transversely 

 oval. Antennae moderate; the ist joint obliquely and laterally 

 truncate ; the flagellum with the joints rather long. Thorax with 

 the parapsidal grooves distinct but not impressed. Scutel ele- 

 vated. Carinate areas of the metathorax mostly distinct. Abdo- 

 mem sessile, elongate ; joint i long, flattened, subolong ; joint 2 

 much shorter ; the rest slowly shorter and shorter. Venter exca- 

 vated. Ovipositor . Legs slender, moderately long ; spurs 



1,1,0; claws pectinated, the pulvillus shorter than the claws. 

 Wings moderate ; radial area and stigma rather short ; areolet 

 triangular, small ; ist recurrent vein angulated ; the 2d recurrent 

 vein almost straight, slightly convex externally. Bullae 3, B, CD, 

 and E ; B normal, small, and indistinct ; CD occupying the mid- 

 dle of its vein, and E pretty near to the angle of its vein. 



Difters from Periope^ Haliday, by its sessile (not subpetiolated) 

 abdomen, its flat (not protuberant) face, and its spurs 1,1,0 (not 

 I, 2, i). And from Exyston^ Schiodte, by its sessile (not petio- 



