J. B. Hatcher — Recent and Fossil Tapirs. 163 



of both of these species. (Compare fig. 3, plate II, of the 

 present paper with A. & B., fig. 1, of Wortman and Earle.) 

 From these and other characters P. simplex appears to have 

 been the ancestor of P. validus and P. obliquidens. There 

 seems to be little doubt that the former is a direct successor of 

 P. si?nplex, while the latter has been derived from that species 

 either directly through P. validus or some other as yet 

 unknown form with all its characters intermediate. 



The Skull : In many respects the skull of Protapirus resem- 

 bles that of the recent Tapir, especially of Tapirus roulini, 

 the least specialized of all the species of modern Tapirs. In 

 the type specimen of P. validus the occipital condyles are 

 sessile and as deep as broad. The condylar foramen is placed 

 well forward and inward just opposite the base of the paroc- 

 cipital process, which is a slender, styliform bone directed 

 straight downward much as in Tapirus roidini, but quite dif- 

 ferent from T. indicus, in which species this process is broad 

 and flat with its distal end curving inward. The post- 

 tympanic process is low and broad and is confluent but not 

 coossifled with the paroccipital process ; its lower extremity is 

 curved forward, abutting against the post-glenoid and entirely 

 enclosing the meatus auditorius externus, a condition not 

 present in any of the living Tapirs. The post-glenoid process 

 is low, broad and thin, and curves forward interiorly ; it is set 

 obliquely to the longer axis of the skull, at an angle of about 

 45 degrees, much as in all the species of recent Tapirs. The 

 zygoma is slender, only slightly expanded, and nearly parallel 

 with the longer axis of the skull. There is no post-orbital 

 process on the malar. The floor of the orbit is much deeper 

 than in Tapirus, bat not quite so deep as in some specimens of 

 Tlasmognathus. The infraorbital foramen is situated well in 

 front of the orbit, and directly above pm. 4, at the bottom of 

 a deep groove, which commences just above pm. 2 and runs 

 obliquely backward and upward, from this point, until reaching 

 the fronto-maxillary suture, where it turns abruptly backward 

 and terminates at the post-orbital process of the frontal. This 

 groove is, perhaps, homologous with a similar excavation on 

 the surface of the skulls of modern species of Tapir. In recent 

 Tapirs it is deepest at, or near, the base of the nasals, and its 

 function, as has been shown by Parker,* is the lodgment of a 

 cartilaginous air sinus ; it very likely served the same purpose 

 in Protapirus ; the apparent and actual change in its posi- 

 tion having been accomplished by the shifting of the nasals to 

 a more posterior position in recent forms. The greatest depth 

 of this groove, in Protapirus, is at a point just opposite the 



*See: Some Points in the Anatomy of the Indian Tapir, by W. N. Parker, 

 P. Z. S., 1882, pp. 768-m. 



