-MORPHOLOGY OF CKAXIAL MUSCLES IX SOME VEUTEBILVTES. 255 



the branchial interarcuales ventrales. There is no hoinologue 

 in the mandibular .segment. These longitudinal muscles 

 possibly date from a period where there were no median 

 cartilages connecting the ventral ends of the liyoid and 

 branchial bars, and formed a rectus system of the head 

 serially homologous with that of the body, though now 

 covered over by the latter, owing to its extension forwards 

 into the head. 



Text-fig. 7U. 



n*j|jc>ln, S& "V niv 



buuiv. 



v\, {rax 



70. 



Lacerta. emlnyo 8 mm., transverse section. The right side of 

 the section is a little anterior to the left. 



(1) Transversi Ventrales, Mm. ]\Iargiuales, and 

 Obliqui Ventrales. — In Scyllium, Acanthias, Sauropsida. 

 rabbit, and pig, the hypobrauchial cranial muscles are the most 

 ventral ones formed from the branchial niyotomes; no trans- 

 versi ventrales are formed. This is also the case in the first 

 branchial segment of Anuran tadpoles, the first, second, and 

 third of the Necturus and Triton, the first and fourth of 

 Ceratodus, the first and second of Polypterus Senegal us. 



