1895. PROCEEDINGS OF THE NATIONAL MUSEUM. 127 



ou the lateral and dorsal border; hamules having the internal branch longer and 

 the external shorter; substylar piece [ = inferior appendage] narrower. Wings 

 transparent, with the veins red and the base a little spotted with reddish yellow; 

 pterostigma smaller, ferrugiueons ; ten to eleven veins in the first costal space; 

 membranule reddish, a little obscure. 



These differences hold good for the j)resent specimens. The size of 

 T. erythnva is: Total length, male, 37-41.5; female, 33-38; abdomen, 

 male, 23-27.5; female, 20.5-25.5 ; hind wing, 26-30.5, pterostigma, 3.5-4. 

 The fifth abdominal segment at aj^ex measures nearly 4 mm. in T. cry- 

 thra'cij 2 mm. in T. ferrugaria. The internal hamular branch does not 

 appear to me to be longer than in T. erythra'a, but the external brauch 

 is proportionately shorter. A figure of the genitalia of a male speci- 

 men of T. ferrugaria accompanies this paper. A similar figure for T. 

 erythra'a accompanies my report on the Odonata of the United States 

 Eclipse Expedition to the Congo. 



The female of T. ferrugaria, may easily be distinguished from that of 

 T. erythrwa, as the latter has the vulvar lamina more nearly at right 

 angles to the abdomen and reaching backward no farther than the 

 middle of the ninth abdominal segment. 



A comparison of specimens of T. ferrugaria and T. erythrwa with the 

 generic characters given by Mr. Kirby^ for Trithemis and Grocothemis, 

 to which these species are respectively referred by him,^ shows the only 

 diftereuce to be that Trithemis has the "abdomen moderately slender," 

 while Crocothemis has the "abdomen stout." I have not been able to 

 detect any other generic character between these two species. In 

 view of their close relationship, as shown above, the claims of Crocothe- 

 mis to generic rank may well be doubted. 



Genus ORTHETRUM (Newman) Karsch. 



The three following species agree with the characters laid down for 

 Orthetrum by Dr. Karsch,^ viz : 



Last antecubital continuous, hind wings with only one cross vein in 

 the median space, sectors of the arculus distinctly stalked, Ijasal side 

 of the cardinal cell [i. e., discoidal triangle] in the hind wings in the 

 prolongation of the arculus; nodal sector strongly waved beyond the 

 middle; membranule large, vertex in the male distinctly bifid, discoidal 

 field of the front wings of three to five rows of cells varying according 

 to the size of the species; sides of the eighth abdominal segment in 

 the female dilated, frons anteriorly fiat, shieldlike, marginate; abdo- 

 men thin, often very slender, often swollen at the base; hind tibite 

 with a few (5-8) widely separated, very strong spines on the outer, 

 under side. 



Dr. Karsch adds that the upper sector of the triangle in the hind 

 wings arises on the outer side of the triangle always distinctly removed 



' Trans. Zool. Soc, I^ondon, XII, pp. 278, 279, 1889. 

 -Cat. Odou.,pp. 19, 21. 

 3Ent.Nach.,XVII,p..58. 



