320 TILE LOWER JAW OF AN AXTHROPIOD APE. [Dec. 1914, 



text-fig. 1 c, p. 317). Here it is necessary to remember that the pit 

 on the inner or posterior face of the symphysis is nearly filled by 

 secondary bone developed in the tendon at the origin of the genio- 

 hyoid muscles. The postero -inferior outline to be compared is, 

 therefore, indicated by a dotted line in the figure. Allowance 

 being made for this, the resemblance is seen to be remarkably close 

 — the anterior face in Heidelberg Man being only steeper, and 

 the digastric insertion now facing more directly downwards. 



The mandibular symphyses of Mesopithecus, Dryopithecus, and 

 Homo heidelhergensis form, indeed, a gradational series (text- 

 fig. 1 a, b, & c), in which there appears to be no place for a stage- 

 resembling that of an}" adult existing Ape. It is difficult even 

 to understand how Eoantliropus (text-fig. 1 e) can be one of the- 

 series. If the outlines of Eoanthropus and Homo Iteidelbergensis 

 be superposed (text-fig. 2 a, p. 319), it will be observed that the 

 former differs from the latter in the specialization of the lower 

 border towards that of a modern Ape. If the outlines of Dryo- 

 pithecus and Homo lieidelbergensis be superposed (text-fig. 2 b), 

 the difference is seen to lie mainly in the reduction of the tooth- 

 bearing region in the latter. On theoretical grounds, the second 

 form of reduction seems the more likely to have taken place. 



Hence, so far as the mandibular sjinphysis is concerned, the 

 Miocene Dry opitli ecus resembles the large modern Anthropoids- 

 no more closelv than it aerrees with the earliest known true Man. 

 By slight changes in two different directions it may have passed 

 into the one as readily as into the other. 



EXPLANATION OP PLATE XLIV. 



Dryopithecus fontani Lartet; left mandibular ramus and symphysis, natural 

 size. — Upper Miocene ; Seo de Urgel, Lerida (Spain). 



Pig 1 . 1. Upper view, showing crowns of molars. 



2. Inner view, showing cross-section near symphysis. 



3. Outer view of molars, showing cingulum. 



4. Lower view showing symphysis and digastric insertion. 



5. Inner view of symphysis, showing pits for origin of geniohyoid and 



genioglossal muscles, d. = insertion of digastric nrascles ; m. 1-3 

 = molar teeth. 



Discussion. 



Mr. E. B. Newton" said that he was of opinion that the terms 

 Pliocene and Miocene, or those of any of the other great 

 periods, so frequently applied in palaeontological research- work, 

 were inadequate for accuracy, and that it was necessary to quote 

 the particular stage of those rocks which had yielded the material 

 described. He instanced the Pikermi Beds, which were often 

 referred to the Lower Pliocene, whereas they belonged to the 

 latest stage of the Miocene, known as the Pontian. To the 

 same part of the Miocene would belong the specimen described 

 by the Author, on account of its association with Hipparion. 



