OSTEOLOGY 143 



than is actually the case). It will be seen, however, that in 

 a skeleton this measurement can never be accurately taken, 

 for the palmar pad is then always missing. In working on 

 skeletons, therefore, it seems that the best way to arrive at 

 the functional length of the fore limb is to consider this as 

 consisting of the sum of the length of the humerus and the 

 length of the radius. Unless accompanied by a phrase of 

 qualification, this will always be considered as constituting 

 the functional length of the fore limb when referring to 

 skeletal characters in the present paper. 



In any work concerning the comparative length of the 

 limbs of mammals it is necessary to have another standard 

 with which to compare the legs, and this can be neither the 

 total length, nor the vertebral length, for the heads or tails 

 of two dissimilar mammals may be short or long, respec- 

 tively. The best measurement for comparison would there- 

 fore seem to be the body length, comprising the sum of the 

 lengths of the cervical, thoracic, lumbar, and sacral verte- 

 brae, and it should be understood that this is meant by body 

 length when hereafter referring to skeletal matters. 



Among the skeletons available there are eight of Homo- 

 dontomys, only three of which are partially articulated, 

 there are three Neotoma, all articulated; and there are four 

 Teonoma, two being articulated. Practically none of these 

 is perfect in every respect, and hence the series is not suffi- 

 ciently large for the average to be dependable. The figures 

 and slight differences should not, therefore, be considered as 

 absolutely accurate; but the trends are undoubtedly trust- 

 worthy. 



In the only three instances where this functional length 

 of the fore leg could be calculated for Homodontoniys it was 

 found to average 44.4 (42.6 to 45.5) per cent of the body 

 length; in three Neotoma 49.3 (48 to 51.6) per cent; and in 

 two Teonoma 47.1 (46 to 48.1) per cent. The subgenus 

 Neotoma thus exhibits a slight trend toward a longer fore 



