NATURAL SCIENCES OP PHILADELPHIA. 



397 



reduced to a short line above. 12th. The dorsal markings of the abdomen 

 are similar, but very much wider and continuous to the middle of joint 8. 

 13th. The vulvar lamina terminates in two robust, approximate, conical 

 branches. Antecubitals 13 15 ; postcubitals 9 11. Two discoidal cellules, 

 commencing with 2 in the front wings, with 3 on the hind wings. 



The $ differs in the same way, except that the vitta on the dorsum of the 

 abdomen is interrupted at the tips of joints 6 and 7, and is narrower than in 

 9 The abdominal appendages are precisely like those of (J 1 jluvialis, except 

 that the hemispherical excavation at the tip of the lower ones is obsolete. 

 Antecubitals 11 13 ; postcubitals 9 11. 



Length J 4748 mill. 9 4850 mill. Expanse <? 6567 mill. 9 7073 

 mill. Pterostigma 3^ 4 mill. Four tf, eight 9 



The following measurements of the six new Gomphi previously described 

 have been taken from single specimens ; and for the sake of comparison I 

 have added those of some allied species, for which, except that of fratemus, I 

 am indebted to the Monographic. The figures represent millimetres. 



CoRDULEGASTER OBLIQUU8, Say Q. ANAX JUNIUS, Drury ! J3SCHNA CLEPSY- 

 DRA, Say <-f $! [9 undescribed.] jEschna constricta, Say! jEschna heros, 

 Fabr. ^Eschna pentacantha, Ramb. $ 9i [ not hitherto found north of Loui- 

 siana; 9 undescribed.] 



ODONATA (LIBELLULINA.) 



Macromia Illinoiensis, n. sp. 9 Brown. Head with the vertical vesicle bi- 

 lobed, the lobes divaricate, each forming an equilateral triangle ; antennae 

 black ; front prominent, laterally contracted towards its summit, deeply exca- 

 vated above, the angulation of the superior with the anterior surface much 

 rounded off except at the sides, above black with violet reflections, with four 

 separate, basal, obtrigonate yellow spots, two outside the excavation, two inside 

 the anterior surface, with its upper half brown and its lower half yellow, the 

 latter enclosing the two usual transverse strise, which are widely and deeply 

 impressed, but not acute; epistoma and labrum of a paler semi-transparent 

 brown, the latter with a wide obtuse longitudinal carina, and obscurely yellow 

 towards its tip in the middle, its anterior edge brown; tips of the mandibles 



1 1 give this figure just as I find it, but I am pretty sure there is gome clerical or typographical 

 error here, and that 41 should be replaced by 7J. Macr. robustus cf, a species of the same size 

 within a millimetre or two, is said to have ire posterior femur 7% millimetres long, and it is diffi- 

 cult to see how a Gompbine as large as this, with the posterior femur only 41 millimeters long, 

 could have a hind leg extending to the middle of the third abiominal segment, which is given 

 as one of the characters of the subgenus Macrogomphus. Unfortunately in tho thirl species of 

 Macrogomplius (annulatus) the dimensions of the posterior femur are omitted. 



1862.] 



