3+ THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
development, there is little in the legs by which to distinguish the present family 
as a whole from the other Siphonaptera. The mid coxa is very narrow in all the 
species of Sarcopsyllidae. The posterior portion of the hind coxa is reduced, becoming 
gradually narrower apically in Hectopsylla and Echidnophaga and being apically excised 
in Dermatophilus, the coxa, therefore, being widest near the base. The tibiae have 
usually no bristles on the lateral surfaces, or only one or two. The legs of the various 
species of Sarcopsyllids have no other characters in common. It is not possible, however, 
to mistake the leg of a Sarcopsyllid for that of any other Siphonapteron. Each genus 
has a sharply characterized type of leg not met with in genera other than Echidno- 
phaga, Dermatophilus, and Hectopsylla, these genera differing in the legs not only from 
one another, but each from all the other Siphonaptera. The general trend of the 
development of the legs is again reduction, but rather reduction in width than in 
length. The legs become the more slender the more they are specialized, the 
number of segments composing the Sarcopsyllid leg remaining the same as in other 
Siphonaptera. The power of jumping is reduced, being entirely lost in the pregnant 
of Dermatophilus and probably in Hectopsylla. The bristles of the legs are in the 
most generalized type of a Sarcopsyllid similar to those of Pulex irritans, pallidas, 
leporis, etc., their number and width becoming less and less in the specialized forms. 
Some of the bristles are prolonged, which is suggestive of the long tarsal bristles of 
some members of the genus Pulex, for instance, P. cleopatrae. 
The number of bristles on the forecoxa is never large, being largest in some 
Echnidnophaga and smallest in Hectopsylla. There are some rather numerous but 
very short and stout bristles scattered over the surface of the forecoxa of Derma- 
tophilus penetrans not found in the other two genera. Similar short bristles are 
situated also on the mid and hind coxae and the femora of Dermatophilus penetrans. 
These bristles are longer in the $ than in the The mid coxa is distinctly more 
ovate in Dermatophilus than in the other two genera. There are posteriorly at the 
apex of the mid and hind coxae either two bristles (as in some Echidnophaga) or only 
one. 
The hind coxae of the genera are very different in shape and armature. In 
Hectopsylla they are simply truncate at the apex, bearing at the apical margin and near 
the anterior edge a number of bristles more or less arranged seriately. In Echidno- 
phaga the hind coxa (PI. I, Fig. 7, 8) is apically produced into a truncate, strongly 
chitinized, process, and on the inner side of the coxa there is a patch of short spine- 
like bristles, such as are often met with among Pulicidae, the bristles being only more 
numerous in Echidnophaga. There is no trace of this patch in Hectopsylla. A 
similar, but less strongly chitinized process, is found in Dermatophilus, this genus lack- 
ing, however, like Hectopsylla, the patch of short bristles, and having the process more 
pointed than it is in Echidnophaga. On the other hand, there is a peculiar specialization 
in the trochanter and femur of the hind leg of Hectopsylla. 
