MORPHOLOGY OF CRANIAL MUSCLES IN SOME VERTEBRATES. 197 



he thoug-lit, was secondary to the first. "Die Monimostylie 

 allgemein von der Streptostylie ableitet.'^ 



The development of the mandibular muscles in the Sau- 

 ropsida sug-gests that in them there are two streptostylie con- 

 ditions — a primary streptostylie pterygo-quadrate in birds, 

 and a secondary streptostylie quadrate in Lacerta vera, 



Text-fig. 23. 



^0X4/^'^ 



^>\.6r^^A^U^, ieg . 



ruA- vru^ 



;^vtlt^-nvo-«^A • 



Lepiclosteus, embryo 8 mm., transverse section. 



Ehiptoglossa, and Ophidia, and that the monimostylie con- 

 dition of Chelonia, Crocodilia, and Rhyncocephalia was 

 developed — and probably independently — from a primitive 

 streptostylie pterygo-quadrate which has been preserved in 

 Birds (loc. cit.). 



The development of the mandibular muscles in Amphibia 

 and Ceratodus affords no evidence that the monimostylie con- 

 dition there present has been derived from a streptostylie 

 one, and a fixed quadrate would appear to be a necessary 



