1 8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



fossil forms will be found in which the characters of face, braincase, 

 jaws and teeth are so generalized as to represent a structure that could 

 have given rise to the distinguishing features of both Hominidce and 

 Pongidce. But nothing could be more contrary to the conditions 

 present in all living and fossil Anthropoidea now known than the 

 simultaneous occurrence in a pleistocene or recent genus of fully 

 developed fundamental characters elsewhere diagnostic of the two 

 groups. 



Summary 



The Piltdown remains include parts of a braincase showing funda- 

 mental characters not hitherto known except in members of the genus 

 Homo, and a mandible, two lower molars, and an upper canine show- 

 ing equally diagnostic features hitherto unknown except in members 

 of the genus Pan. On the evidence furnished by these characters 

 the fossils must be supposed to represent : either a single individual 

 belonging to an otherwise unknown extinct genus (Eoanthropus), 

 or two individuals belonging to two now-existing families (Homi- 

 nidce and Pongidce). The fossils are so fragmentary that their 

 zoological meaning will probably remain a subject of controversy. 

 Yet the weight of the difficulties on the two sides is unequal. 

 In order to believe that all the fragments came from a single indi- 

 vidual it is necessary to assume the existence of a primate differing 

 from all other known members of the order by combining a brain- 

 case and nasal bones possessing the exact characters of a genus 

 belonging to one family, with a mandible, two lower molars, and an 

 upper canine possessing the exact characters of a genus belonging to 

 another. Thus must be associated in a single skull: (a) one type of 

 jaw with another type of glenoid region, (b) one type of temporal 

 muscle-origin with another type of temporal muscle-insertion, (c) 

 a high degree of basicranial adjustment to the upright position with 

 absence of that corresponding modification in the lower jaw called for 

 by all that is now actually known of the structure of the braincase and 

 mandible in primates, and (d) a protruding lower jaw with a form 

 of nasal bone not elsewhere known except in connection with a 

 retracted upper dental arch. In each instance the opposed char- 

 acters are sharply defined and easily recognizable in the fossils ; while 

 in no single feature is there any trace of the blending of the two types. 

 On the other hand the assumption that the skull and jaw belonged 

 respectively to a man and a chimpanzee carries with it only two diffi- 

 culties : (a) that of the deposition within a few feet of each other of 

 the remains of two animals whose bones are rarely found in gravel 



