NATURAL SCIENCES OF PHILADELPHIA, 399 



costa ; the ferrnginous basal stripe, between the costal and subcostal, is only 

 half as long; costal vein in all four wings yellow to its extreme tip ; triangles 

 all with one cross-vein. Antecubitals 17 18; postcubitals 10 11; two discoi- 

 dal areolets, commencing with three in all the wings. 



Length 9 69 mill. Expanse 9 94 mill. Pterostigma 3 mill. Hind femora 

 12 mill. ; hind tibia; 11 mill. One 9 ; $ unknown. Distinct from all described 

 N. A. species, by the yellow costal veins. The front and abdomen resemble 

 those of annulata, Hagen, but the dorsum of the thorax in that species is imma- 

 culate, and the pleura has two yellow stripes. Occurred on the Des Plaines 

 River, near Chicago. 



Cordulia tenebrosa? Say. C. filosa, Hagen, and C. tenebrosa, Say, are evi- 

 dently, from the differences in their <j* abdominal appendages, very distinct 

 species ; and of both these species only the $ is known. The following 9 may 

 be referred with some propriety to either, though I rather incline to the opinion 

 that it is tenebrosa. Probably some particulars may be mentioned below, which 

 may serve either to identify it with Dr. Hagen's species, or to separate it ef- 

 fectually. 



The abdomen is shaped quite differently in $ $ Cordulia lateralis, Burm., the 

 $ abdomen having a strong constriction on segment three, after which it ta- 

 pers to the tip ; and the 9 abdomen having no constriction whatever, but ta- 

 pering gradually from base to tip, and being much wider and more depressed 

 than the <^\ I presume that the same distinction prevails in other species of 

 the genus, and that the abdominal constriction noticed both in filosa, Hagen, 

 and in tenebiosa, Say, is merely a tf sexual character. Again, the 9 9 f C. 

 lateralis, have almost always hyaline wings, but I have a single, immature 9 

 specimen, captured at the same time and place with many maturer individuals, 

 with hyaline wings, which has the wings partly fumose ; and C. albicincta, ac- 

 cording to the Synopsis, has the anterior margin of 9 wings subflavescent, 

 while the $ has hyaline wing3. The marginal flavescence on the wings of my 

 9 ought not, therefore, to afford any reason for considering it distinct from 

 either Dr. Hagen's or Say's ^f , both of which have hyaline wings. 



9 Obscure, brassy green. Vesicle of the vertex obviously punctured, 

 with long, dense, black hairs, truncate-triangular, its tip with an impressed 

 longitudinal indentation extending half way to its base, brown at tip, 

 black with a slight brassy green reflection at base ; antennae black ; front 

 coarsely and confluently punctured above, on the upper two-thirds of its ante- 

 rior surface with very coarse punctures mixed with ruga?, the punctures lower 

 down becoming obsolete; the punctate surfaces bright, brassy green, bordered 

 laterally and anteriorly with a yellow line, the anterior yellow line straight ; 

 the rest of the front, the epistoma and the labrum semitransparent obscure 

 greenish; labium yellowish. Dorsum of thorax, with the carina yellowish, 

 otherwise immaculate ; pleura somewhat polished, with blue reflections, and 

 with two distinct yellow stripes, one before the spiracle, slightly abbreviated 

 and narrower, another behind the spiracle much abbreviated above, slightly 

 below, and wider; sternum pale greenish brown. Abdomen a little inflated at 

 base above, and tapering regularly to its tip, where it is blackish ; glabrous and 

 black below the lateral carina, with a large, obscurely defined, yellowish spot 

 on the second segment beneath, and the basal half of the third segment semi- 

 iransparent below, so as to appear yellowish ; joints eight and nine greenish 

 black below the lateral carina ; joint ten triangularly emarginate at its tip for 

 one-half its length. Abdominal appendages long, slender, black, wide apart 

 at base, pilose, opaque, slightly smaller at base, thence cylindrical, till towards 

 the tip they contract and terminate obtusely ; viewed laterally, they curve very 

 slightly downwards ; viewed from above, they curve slightly inwards for quarter 

 their length, and then divaricate slightly in a straight line; superior anal pro- 

 cess very short, semicircular, black, deflexed. Vulvar lamina extending nearly 

 to the tip of joint ten, divaricate with the venter, black, glabrous, polished, its 

 inferior surface a hollow semi-cylinder, with its concavity upwards, rounded at 



1862.] 



