282 
GEO. H. HORN, M. D. 
were bifid, they were not so in any American form that he had seen. 
It seems to me that a careful homological study of the claws shows 
that in all our species these members are either bifid, or of a modified 
l)ifid form. While they are usually called cleft, there is no truly 
cleft claw in any species. If we examine the species related to }W- 
litus and those near torpidus, the claws will he found so nearly of the 
true bifid type that they should he called so. Tracing the modifica- 
tions of this form it will be observed that the inner member of the 
bifid tip gradually shortens and broadens, while it preserves its lateral 
position in relation to the other part, although becoming quite a 
broad tooth. 
It seems not to have been noticed that in the group above indicated 
the claws are not only different in the two sexes, but, especially, in 
the male, different on the three pairs of feet. This effectually pre- 
vents anything but the most I’estricted use of the forms of the claws 
in separating either groups of species or species themselves. 
As the descriptions of the modifications of the claw would be an 
unnecessary rei)etition at this time, the student is referred to the 
remarks under each species. 
At this time I desire to acknowledge the assistance received, with- 
out which this essay would have fallen short of its present complete- 
ness. The Museum of Comparative Zoology has permitted the free 
use of the LeConte collection for conq)arison, without which the 
names here used would have less certain value. The National Mu- 
seum, through its Curator, Dr. C. V. Riley, has loaned its material, 
which has in one case removed a doubt from my mind, and in several 
others prevented the necessity of describing from uniques. The 
cabinet of the American Entomological Society has ako been freely 
used. To Messrs. Ulke, Liebeck, Seeber, Wenzel and Henshaw, I 
am indebted for the free use of their material and the gift of speci- 
mens. Finally, to Mr. Fred. Blanchard, of Low’ell, I am under 
especial obligations for his many useful suggestions, and for his hav- 
ing very kindly studied several difficult questions regai’ding the 
of imus senes on the carefully collected material in his cabinet. 
The meaning of the expressions used in the subsequent j>ages of 
the essay having been sufficiently explained, the following table is 
presented to enable the species to be, at least approximately, deter- 
mined. The arrangement of the species by the sequence in the table 
does not in all cases ajjproximate those having a superficial resem- 
blance. The object of this study is to enable the determination of 
