MOEPHOLOGY OF CRANIAL MrsrL[:S IX SOME VERTEBRATES. 295 



Cjvd ill the liyoid segment, innervation of the interarcualis 

 ventralis I (branchio-hyoideus) by the IXth. 



On the other hand, Mammals resemble Sauropsida, and 

 differ from Amphibia, in the non-formation of levatores 

 arcuum branchialium, and the associated development of the 



Text-fig. 1)3. 





KKvi. Sf>.itv Am. 



^ rU>xlv,3uL 



93. 



trapezius from the upper ends of all the branchial mj^otomes, 

 disappearance of the branchial myotomes (after formation of 

 trapezius and interarcnales ventrales from their upper and 

 lower ends), non-formation of transversi ventrales. 



It has been suggested above in discussing individual groups 

 of muscles that all the first-named features are primary ones, 

 and that all the second-named features are secondary 

 phenomena. It is possible that secondary features may have 



VOL. 56, PAKT 2. NEW SERIES. 21 



