294 



F. H. EDGE WORTH. 



The sig-nificance of such resemblances from a phylogenetic 

 point of vieAV is doubtful, though probably the first two 

 named are by far the most important. 



The ancestry of Mammals has been the subject of inquiry 

 and speculation for many years. Two theories have been 



Text-fig. 92. 



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92. 



held — one, that Mammals are descended from Sauropsida, 

 the other, that they are descended from Amphibia. 



As regards the cranial muscles, Mammals resemljle 

 Amphibia, and differ from Sauropsida in the following 

 particulars: non-division of the mandibular myotome into 

 dorsal and ventral parts, formation of a hyo-maxillaris 

 (anterior digastric), non-formation of a dorso-ventral sheet 



