234 F. H. EDGEWORTH. 



is used for tlie longitudinal muscles passing- between the 

 ventral ends of the branchial bars. 



The foremost " interarcualis ventralis" passing from the 

 fii'st branchial to the hyoid bar has received many names, 

 e. g. ceratoidien lateral on ])etit ceratoidien (Cuvier), inter- 

 cornalis (Owen), cerato-hyoideus internus (Fiirbringer, Miss 

 Piatt, Driiner), cerato-hyoideus (Osawa), hyoideus lateralis 

 (Bendz), kerato-hyoideus (Ellenberger and Baum), inter- 

 hyoideus (Dubois), kerato-thyro-hyoideus (Jaquet). The 

 name " branchio-hyoideus " was applied to this niuscle in 

 Sphenodon (ioc. cit.), and is employed in the case of other 

 animals, when it occurs, in this paper. 



In Scyllium, van Wijhe described the coraco-branchialis 

 and coraco-mandibularis as developing from the walls of the 

 obliterated anterior prolongation of the pericardium, and 

 from " Nebenzweige," given off from the " Unterendeu der 

 Wande der Yisceralbogenhohlen." 



It will be shown later (p. 268) that the coraco-mandibularis 

 and coraco-hyoideus are developed from the fourth to eighth 

 trunk-myotomes. The five branchial myotomes form at first 

 epithelium-lined cavities continuous below with the cephalic 

 coelom (Text-fig. 2). They separate from the cephalic coelom 

 in 14 mm. embryos, and their cavities become obliterated 

 (Text-fig. 4). In 17 mm. embryos the lower ends of the 

 branchial myotomes grow backwards, and become cut off 

 from the remainder of the myotomes, forming coraco- 

 branchiales (Test-figs. 8, 10). The (now) ventral ends of the 

 myotomes grow downwards outside the Anlagen of the 

 coraco-branchiales forming the ventral ends of the constrictor 

 (Text-fig. 13). The upper ends of the myotomes, in embryos 

 between the lengths of 17 and 20 mm., increase in antero- 

 posterior extent (Text-fig. 14), and, fusing together, extend 

 backward as the trapezius' to the shoulder-girdle. Below 



' It is stated by van Wijhe tliat the seventh, eig-lith and ninth 

 myotomes give rise to " Voni Schiidel ziim Schultergurtel ziehende 

 Muskeln nebst deni vordevsten Theile des sterno-hyoidens," but the 

 trapezius is not specifically mentioned by him. 



