lOO NERVE COxMPONENTS OF BONY FISHES. 



Chimaera, in most selachians, in ganoids, siluroids and 

 some other fishes, and accordingly it receives neither 

 lateralis nor general cutaneous fibres. The r. pre-tremati- 

 cus is also totally wanting. The ramus post-trematicus 

 is, however, identical with the corresponding branches of 

 the several branchial trunks of the vagus. The nomen- 

 clature employed for the branchial musculature and for 

 the cranial musculature in general is that of Vetter ('78). 



The motor IX fibres from the ri. ambiguus run along 

 the ventral side of the root and at the ganglion they 

 separate slightly from the latter ventrally, to rejoin the 

 nerve beyond. The motor component in this region just 

 below the ganglion gives off fibres for the first m. levator 

 arcus branchii internus (/. /. a. i.). Just beyond the 

 ganglion a very minute pharyngeal ramus {ph. IX) is 

 given off from the fine-fibred component for the mucosa of 

 the roof of the mouth above the first gill, then a minute 

 motor twig for the first levator arcus branchii externus 

 (/. /. a. e.). 



All of the remaining fibres enter the first gill, just 

 before entering which they divide into two nearly equal 

 ramuli, a dorsal and a ventral. The latter contains all of 

 the remaining motor fibres and a somewhat larger number 

 of fine communis fibres, passes down the outer or convex 

 surface of the ceratobranchial bone and supplies the 

 muscles of the gill filaments and their mucous surface. It 

 lies dorsally of the first demibranch and probably distrib- 

 utes most of its fibres to it. The dorsal ramulus pursues 

 a course parallel to the last, but on the opposite, or con- 

 cave side of the ceratobranchial bar, distributing to the 

 large taste buds with which this dorsal surface of the gill 

 is plentifully supplied and to the long gill rakers. Prob- 

 ably many of its fibres supply the general mucous surface, 



