MOKPHOLOGY OF CRANIAL MUSCLES IX SO:\FH VEETEBEATES. 245 



arcufiles recti aud obliqui by Driiner. The trapezius is a 

 capiti-dorso-scapularis; it is formed by proliferation from the 

 outer surface of the fourth levator in 8.^ mm. (just hatched) 

 larvae. 



Driiner described in Urodela a first, third, fourth, and fifth 

 transversus ventralis (called by him " interbranchial ") in the 

 territory of the first, third, fourth, aud (an atrophied) fifth 

 branchial arches. He also stated that the first is formed by 

 a secondary attachment of the ventral facial muscles to the 

 first branchial arch — this, which is not a true transversus, is 

 described above (p. 215). In Necturus and Triton cristatus 

 a transversus ventralis III is not formed; there is only a 

 lA^th. The question Avhether the laryngei represent a Vth 

 is discussed below. The transversi ventrales were included 

 by Driiner in the ventral head muscles, but they are not 

 serially homologous with the iutermandibularis aud inter- 

 hyoideus, which are developed from the walls of the cephalic 

 ccfilom in the mandibular and hyoid segments, whereas the 

 transversi ventrales are formed by downgrowths of the 

 bi-anchial myotomes dorsal to the cephalic coeloni. 



In Rana temporaria the ventral ends of the four 

 branchial myotomes separate from the parts above in 6^ mm. 

 embryos, and form the Anlagen of the four interarcuales 

 ventrales, and in the second, third, and fourth segments the 

 Anlagen of the transversi ventrales. In the first three seg- 

 ments the middle portions of the myotomes form the ]\[m. 

 marginales and the upper parts the levators. The portion 

 of the fourth myotome above the iuterarcualis ventralis forms 

 the fourth levator, no M. marginalis being developed. 



The median ends of transversi ventrales II aud III become 

 attached to the posterior surface of a ventral projection of 

 the iirst basibranchial (second copula), and their lateral 

 edges to the processus branchialis. The lateral edges of 

 transversus ventralis IV become attached to the fourth cerato- 

 branchial (Text-fig. 61), and their median edges meet in a 

 central raphe, which underlies the fore part of the larynx. 

 There are similar muscles in larvas of x\.lytes, Bufo lenti- 



