104 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
in mind by those using them that the apparent shape of the appendages 
of the males depends very largely on the particular angle at which they 
are viewed, and that the appendages themselves are capable of a consid- 
erable degree of rotation. The seeming differences between the two 
figures of Argia tibialis, Plate 2, Figs. 7, 74 and 8, 8a, are readily ex- 
plained in this way, as any one who will compare them with a male of 
this species may convince himself. Yet no one who has attempted the 
stady of this difficult genus will question the value of the aid which 
these figures offer in elucidating the species all too briefly described in 
the Synopsis of 1865, remembering also that their originals are scattered 
through several museums of Europe and America. The arrangement of 
these illustrations on the plates has been chiefly guided by two ideas : 
to place similar shapes near together for ease of comparison, and to 
associate species which from personal knowledge are believed to be 
related. 
It has been thought desirable to accompany these figures with a list 
and bibliography of all the known species of this group. The list has 
been arranged alphabetically for convenience’ sake, since the writer has 
too little acquaintance with the South American species to attempt to 
place them in their proper relationships, while, on the other hand, for 
reasons given elsewhere, he cannot subscribe to the classification em- 
ployed in the Synopsis of 1865. It is hoped that the bibliography 
embraces references to all descriptions and figures, but mere locality 
lists are not necessarily included. The distribution of each species is 
given in a general way; details will be found in the authors quoted, 
Two works which together contain descriptions of all the known species 
are cited in abbreviations. These are: De Selys-Longchamps, Synopsis 
des Agrionines, 5me légion : Agrion, Le grand genre Argia (Bulletin Acad. 
Roy. Belg. — 2— XX., pp. 375-417, 1865), which is quoted simply as 
“ Argia;” since the paging of the separate copy is different, the page 
number of this latter is also given, but in parentheses (). While this 
Synopsis is published as under the authorship of De Selys, many of the 
descriptions were written by Hagen, and in such cases due credit is 
given to the latter. The other work is Calvert : Odonata in Biologia 
Centrali-Americana, Neuroptera, pp. 17 et seg., London, 1901-02, here 
shortened to ‘B.C. A.” 
As far as possible, the present location of the types of each species is 
given from personal knowledge and from the literature. 
The two closely related genera Hyponeura and Onychargia have been 
included. 
