The picture of the differences between _Tympanuchus_ and _Pedioecetes_ that the present study presents is radically different from that presented by the study of Hudson, _et al._ (1959). These authors reported the following differences between these two genera. (I am using my terminology.) The origin of M. piriformis is narrower in _Pedioecetes_ and is more posteriorly situated; the belly of M. extensor iliotibialis anticus is broader in _Pedioecetes_; the belly of M. tibialis anticus is longer; the belly of M. peroneus brevis is shorter; the insertional tendon of the anterolateral head of M. flexor perforatus digiti III is shorter; the belly of M. flexor digitorum longus is shorter; only two (rather than three) of the branches of M. extensor digitorum longus on the tarsometatarsus are ossified; the posterior metatarsal crest is shorter; M. flexor perforans et perforatus digiti II has two heads in _Pedioecetes_ but only one in _Tympanuchus_; the roof over the hypotarsal canal enclosing the tendon of M. flexor digitorum longus is bony in _Pedioecetes_ but fibrous in _Tympanuchus_; M. flexor cruris lateralis is wider in _Pedioecetes_; and the origin of M. femorocruralis is wider. I paid particular attention in my study to these 13 features given by Hudson, _et al._; of these the only differences that I found to be constant were the last two. The apparent reason for this great discrepancy is the small number of legs of _Tympanuchus_ studied by Hudson, _et al._ They studied eight legs of _Pedioecetes_ but only two legs of _Tympanuchus_. This emphasizes the danger of making comparisons based on a very small number of specimens (a criticism which may prove to apply to the present study as well). The reason why Hudson, _et al._ did not report most of the differences found by me is not so apparent. Either the specimens studied by the former workers showed a greater variation in these characters than did my specimens or else those workers overlooked the differences. Probably both factors are involved. It remains to be determined how many specimens need to be studied in order to obtain a fairly accurate picture of variation. _Comparison with Other Studies of Innervation_