SCOTT : LITOPTERNA OF THE SANTA CRUZ BEDS. 3 1 



mt. Ill longer, but he does not state that manus and pes were derived 

 from the same individual. Metatarsal IV is very like the corresponding 

 metacarpal and its proximal end is hardly at all overlapped by that of mt. III. 



The phalanges resemble those of the manus, but those of the functional 

 digit III are somewhat longer, more slender, more depressed and flattened, 

 while the ungual is decidedly longer, narrower and more pointed than is 

 that of the manus. 



Restoration (PL I). — The chief difficulty in the way of making a satis- 

 factory restoration of Diadiaphorus is the uncertainty as to the number of 

 trunk-vertebrae, which, of course, has an important effect in determining 

 the appearance and proportions of the animal. In general appearance, the 

 skeleton oi Diadiaphorus bears considerable resemblance to that oi Hyra- 

 codon, the lightly built, cursorial rhinoceros from the Oligocene of North 

 America, though an immediately obvious difference is the much shorter 

 neck of the Santa Cruz genus. The head is relatively rather small, though 

 deep and heavy dorso-ventrally, and the very short nasals are especially 

 characteristic of this genus. The neck is short, hardly equaling three- 

 quarters of the basal length of the skull, and quite slender, which is due 

 to the small size of the vertebrae and the shortness of the neural spines, 

 save that of the axis. 



For reasons that have been sufficiently explained in the foregoing pages 

 (p. 10), it has been assumed that the number of trunk-vertebrae was 21, of 

 which 15 have been assigned to the thoracic and 6 to the lumbar region. 

 The back appears to have been nearly straight, without hump at the 

 shoulders, and with rather short and slender spines. The thorax was 

 probably long and the loins rather short. The caudal vertebrae are still 

 quite unknown, but from the character of the sacrum it is evident that the 

 tail was short. 



The limbs are moderately elongate and slender and resemble much 

 those of the three-toed horses, such as Protohippus. The humerus is 

 rather short and the fore-arm bones, which remain separate, are somewhat 

 longer. Femur and tibia, on the other hand, are of nearly the same length. 

 The tridactyl feet are also elongate, but this elongation is largely due to 

 the length of the phalanges, carpus and tarsus, the metapodials being 

 relatively much shorter than in the horses. Though the feet have three 

 complete digits each, only the median digit touches the ground, while the 

 laterals are mere dew-claws. 



