1901.] NATURAL SCIENCES OF PHILADELPHIA. 139 



Leptagrion macrurum Burm. cf. 7th segment, ant. Brazil. 

 8 (F 6'-8' + n", f 10"-20" + 2'-3'). 



Leptobasis vacillans Selys. 2 c?. 7th segment, ant. Tabasco, 

 Mex. 4 (F 13-15, f 10-12). 



Agriocnemis femina Brauer. cf. 6th segment. Borneo. 

 4 (F 10-15, f 8-10)? 



Hemiphlebia mirabilis Selj$. ?. Victoria. 4 (F 2'-4' + n", 

 f n", F n", f n"). 



Legion G. — Lestes Selys. 



Archilestes grandis Ramb. cf . San Jose del Cabo, Baja Cal. 

 8(Fn). 



Lestes disjundus Selys. 6th segment, New York. 8 (F n). 

 Lestes vigilax Seljs. cJ'. New York. 4 (F n, f n). 

 Lestes leda Selys. d. 6th segment. Victoria. 4 (F n, f n). 

 Lestes ienuatus B^amh. ?. Tepic, Mex. 8 (F n)? 



Intra-genePvIC Variations. 



By an examination of the structural formulae given above it 

 will be seen that a classification into genera based on resemblances 

 in gizzard structure would agree in most cases with that now in 

 use based upon the structure of wings and other extei-nal features of 

 the body. If, for instance, we examine the structural formulae 

 for Sapho orichalcea and S. ciliata, we find very little difference 

 between the two species. In both we see sixteen fields, which in 

 the former are of three sizes, and in the latter of two. But the 

 number and size of the teeth are approximately equal. 



Where a number of species of one genus have been studied, 

 these all, as a rule, show the same number of folds. Exceptions 

 are seen in the genera Hetcerina and Heterafj rion. Of five speciea 

 of Hetcerina examined, four show eight folds of the gizzard lining, 

 and one, americana, four folds, although another specimen of the 

 same species (PI. II, figs. 2 and 3) shows eight folds in both larval 

 and adult gizzard linings; of four species of Heteragrion three have 

 sixteen folds; one, eight. 



Even when they vary in the number of folds, species of the 

 same genus are seen to agree almost invariably in the size and 

 number of teeth on each fold, as well as in the arrangement of 

 these. 



