158 DR. R. W. SHUFELDT ON [Apr. 1, 



III. Of the Myology. 



To assist me in the demonstration of the muscles of this lizard I 

 have at my hand an excellent paper entitled " Notes on the Myology 

 of Liolcjm belli;' by Alfred Sanders (P. Z. S. 1872, p. 154); 

 also one entitled " Notes on the Myology of the Phrynosoma 

 coronntum,''^ by the same author (P. Z. S. 1874, p. 71); also the 

 admirable memoir, " On the Myology of Ohamceleon parsonii" by 

 Professor St. George Mivart (P. Z. S. 1870, p. 850); and finally the 

 more generalized contribution to the study of the muscles in Lizards 

 presented us by Prof. C. K. Hoffmann in Bronn's ' Thier-Reichs ' 

 (45). With these I must likewise mention the studies of Professor 

 Mivart upon the Iguana (P. Z. S. 18(i7) ; and other works on the 

 muscles of reptiles by the same distinguished author. As to the 

 names I here bestow up3n the muscles of the Heloderm, T can say 

 with Sanders, who remarked in his pa|)er on the myology of Liolepis, 

 that " With regard to the nomenclature, it must be regarded as 

 merely a tentative expression of opinion, liable to be changed at any 

 time on the demonstration of error." It is a long day vet before we 

 can say in truth that our knowledge of the myology of reptiles is in 

 any way complete, and a great many forms still remain to be worked 

 out. 



Muscles of the Head. 



1. Mylo-hyoideus anterior. — We find in the present subject this 

 muscle to be but feebly developed ; it arises, on either side, from 

 the inner aspect of the lower border of the ramus of the jaw, for 

 about its anterior moiety, and as far forward as the symphysis. 

 Mesially, it indistinguishably blends with its fellow of the opposite 

 side, making no median raphe. Postero-laterally it faintly overlaps 

 the mylo-hyoideus posterior, while at the midiJle of the throat it 

 almost seems to blend with that muscle : and this delicate, super- 

 ficial plain of transversely disposed muscular fibres overlays a number 

 of the group of the more deeply situated and true hyoidean 

 muscles. 



2. Mylo-hyoideus posterior is a far better developed muscle than 

 the one I have just described, and apart from its greater size it 

 diifers from it in that it exhibits a fairly well-developed medio- 

 tendinous raphe for nearly its entire length. Into this the niuscle 

 of either side merges. Springing from the occiput and the dense 

 fascia at the antero-su[)erior part of the neck, from the mandibular 

 suspensorium, as well as from the inner aspect of the posterior moiety 

 of the mandible itself, the posterior mylo-hyoid sends its fibres, for the 

 most part, transversely to the middle line of the throat, where they 

 blend with the delicate, longitudinal, raphenous line in a manner 

 which 1 have already indicated. The posterior border of this 

 muscle is well-defined and thickened : it crosses the throat just 

 anterior to the region of the chest ; while laterally the hinder 

 margin of an aural aperture is formed by its free muscular edge. 

 Anteriorly it is very thin where it meets the anterior mylo-hyoid m 



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