2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 81 



tip of the discal. The third vein is not always forked near the tip. 

 but this fork occurs in the genotype (mentioned in the note after the 

 description of longicomis, which lacks it) ; it does not occur in the 

 genotype of Exetasis. There is a marked tendency toward the devel- 

 opment of adventitious cross veins, which apparently have very 

 slight taxonomic value. Considerable variation exists in the apical 

 part of the first posterior cell, which may be petiolate or closed in 

 the margin, or partially coalesced with the second posterior by the 

 disappearance of the last part of the fourth vein, or widely open. 

 In drawing up a key largely from figures and descriptions, I had 

 made considerable use of these differences, until I observed that my 

 new species differed in the two wings of the single specimen and 

 would run to what I had supposed were two groups of species. This 

 discrepancy compelled me to view these differences with more caution. 



The nearest related genus is Apelleia Bellardi.^ The only species 

 included was mttata, new, from Mexico; it has bare eyes, and this 

 was put forward as the main difference from Ocnaea. Osten Sacken 

 described in Ocnaea a species {grossa) with bare eyes, indicating 

 that the character is not of generic value; but it seems so to me, and 

 I therefore transfer grossa to Apelleia. I recognize the fact that 

 great caution should be exercised in proposing new genera in the 

 family, where great plasticity seems to exist in characters which 

 would elsewhere be of generic or even familj^ rank. The problem 

 is to find constant characters, and this implies the examination of 

 considerable series in many species — a requirement which can hardly 

 as yet be met in any collection. It may be that Exetasis will ul- 

 timately be restored to rank on the absence of the fork of the third 

 vein; it would include tu7nens Walker (genotype), calida Wiede- 

 mann, and longicomis Erichson. 



In preparing the following key, I have been able to examine only 

 schwarzi^ gig as, falcifer, flavipes, and trivittata (all in type mate- 

 rial) ; Cole's figures and those of Wiedemann, Erichson, Walker, and 

 Osten Sacken have been of great assistance, and I have studied the 

 descriptions closely. Nevertheless it must be considered as a pre- 

 liminary effort. Cole has given a key to the five species from North 

 America, which he had seen, in the reference cited above. I still 

 have misgivings as to the distinctness of m}^ gigas and falcifer, 

 which may be a single unusually variable species. 



In response to a request from me. Dr. G. Enderlein very kindly 

 sent me notes on the types of three species in the Berlin Museum 

 (micans, longicomis, and luguhris), together with excellent figures 

 of the venation in each case. 



« Mem. Acad. Sci. Torino, vol. 21, p. 214, 1861 (or " Saggio di Ditt. Mess.," appendix, 

 p. 17). 



