170 O. C. Marsh—Limbs of Sauranodon. 
five, as shown in the cut below. These correspond to the tar- 
sals, and in the next series are the six metatarsals. There are 
six digits represented in this specimen. The distal phalanges 
are small and circular, and are left unshaded, as their exact 
position has not been determined. 
- Left hind paddle of Sawranodon discus, Marsh; seen from below, 
one-eighth natural size; f, femur; ¢, tibia; 7, intermedium; /’, fibula; J first 
digit; V, fifth digit. 
The above figure agrees essentially with the other paddles 
reserved, and thus may be taken to represent the typical limb 
in this group of reptiles. The most striking features in this 
Sauranodon limb are, the three bones articulating with the 
femur, and the six complete digits. These characters mark a 
stage of development below that seen in any other air-breathing 
vertebrate, and only approached by the limb of Jchthyosaurus. 
he transverse segmentation is distinct in the first five series, 
regarding the humerus and femur as the first segment, or 
propodial bones.* If the three bones of the second series (epi- 
dials) are rightly interpreted, the middle one is the interme- 
ium. Its position in the paddles of Sawranodon of both the 
known species indicates that its true place is in the segment 
where it is found. If so, it follows that in the process of 
differentiation this bone has been gradually crowded out of its 
original position between the marginal bones of the second, or 
ie ah series into the third, or mesopodial, where we now 
nd it. 
* The need of general designations to apply to the corresponding segments alike 
of the anterior and posterior limbs of the air-breathing vertebrates is evident. 
While we have the convenient terms “ Phalanges” and “‘ Metapodials” for the dis- 
tal pa the extremities, there are no names in use for the portions above. 
Hence, the following are suggested : 
Anterior. Posterior. 
Propodial bones = Humerus, Femur. 
Epipodial “ “ Radius and Ulna, Tibia and{Fibula. 
Mesopodial ‘“ 0 Tarsals. 
Me 7 4“ 
~ 
arpals. 
ta “ Metacarpals, ” §Metatarsals. 
Phalangial ,“* ‘“ Finger bones, * Toe bones. 
