418 DAVIDSON BLACK 



sence of the operculum, the somatic levator musculature is 

 plentifully represented and highly specialized. Similarly, in 

 the absence of the operculum no apparent hindrance has been 

 imposed in the way of development of the visceral component 

 of the trapezius complex, and it is significant to note that in 

 the most highly specialized amphibians (i.e., anurans) this 

 \dsceral component has become further elaborated to form two 

 distinct muscles (mm. cucularis and interscapularis). 



With regard to the possible recognition of a sauropsidan 

 prostadium in any amphibian condition of cucularis develop- 

 ment, it is of interest to record that in the tadpole Strong de- 

 tected an anastomosis between vagus and hypoglossus fibers 

 passing to what he considered to be the m. diaphragmato- 

 branchialis medialis of Schulze (v. 53, p. 141). This condition 

 was absent in the tadpole in which metamorphosis had begun 

 and in view of the fact that Schulze (I.e.) considered that the 

 m. diaphragmato-branchialis develops into the m. sterno- 

 hyoideus, its significance in the present connection may be 

 questionable. It provides very suggestive evidence, however, 

 that in anuran ontogeny there may be an admixture of muscular 

 elements derived from both splanchnic and somatic sources 

 within a single effector. 



Among urodeles Fiirbringer (20, p. 265) has denied the exis- 

 tence of a double innervation of the m. capiti-dorso-scapularis 

 (the cucularis muscle in salamandrids) or of the m. dorso-scapu- 

 laris of perennibranchiate forms. On the other hand, McGregor 

 (42) recorded the occurrence of an anastomosis between vagus 

 and hypoglossus fibers in the adult Cryptobranchus alleghanien- 

 sis, but his observations were incomplete and no mention was 

 made of the innervation of the trapezius muscle. 



It has remained for the exact observations of Norris (46) 

 upon the distribution of the vagal and spinal nerves in Siren 

 lacertina to demonstrate beyond a doubt that in this animal, 

 in which so many oddly mixed primitive and specialized char- 

 acters appear, the trapezius muscle receives its innervation from 

 two sources, viz., from a branch of the R. intestino-accessorius 

 X, and from small dorsal branches of the ventral rami of the 



