168 F. H. EDGP]WORTH. 



of their adult forms, butiu some cases it suggests corrections. 



In the case of Lepidosteus only the hypobrancliial muscles 

 have been described — by Fiirbingei*, and the names for other 

 muscles have been as far as possible those used by Vetter and 

 Allis in Ganoids and Teleostei. The cranial muscles o£ 

 Polypterus have been described by Pollard, and the hypo- 

 branchial muscles by Fiirbringer. They did not state the 

 species examined. Those of Polypterus senegalus (speci- 

 mens 7i to 9h cm. long) differ in a few particulars from 

 the descriptions given by those authors. The cranial muscles 

 of Sal mo fario have not hitherto been described, but the 

 researcbes of Vetter in other Teleostei made identification 

 and nomenclature possible. 



Yan Wijhe described the early stages of the development of 

 the cranial muscles of Scyllium ; and Miss Piatt those of 

 Necturus ; observations otherwise have been limited to the 

 development of individual muscles or muscle-groups. 



The nomenclature employed by previous writers has, in 

 general, been followed. In cases where different names have 

 been applied to homologous nmscles in related animals a 

 choice has been made, and this has necessitated some 

 changes. 



The paper is divided into the following sections : (1) The 

 segmentation of the head; (2) mandibular muscles; (3) 

 hyoid muscles ; (4) eye muscles of the rabbit; (5) branchial 

 muscles; (6) CESophageal, laryngeal, and pharyngeal muscles ; 

 (7) muscles derived from trunk myotomes passing to the 

 upper ends of the branchial bars; (8) hypobranchial spinal 

 muscles; (9) lingual muscles; (10) some phylogenetic 

 speculations; (11) on Furbringer's theory of the skull ; (12) 

 a suggested morphological classification of the motor centres 

 of the mid- and hind-brain in man. 



Thk Segmentation oi' the Head. 



In the body region of Scyllium embryos it is found that 

 there is an unsegmented part below enclosing the ccelom, and 



I 



