246 H. W. NORRIS 
AD The first: branchialenerv.es.. ac oe ee ie fe oe eee eee 308 
5. The rami supratemporalis-et auricularis X.......0. 0.5. +o eee 312 
6) The second branchial merviesser sen a soe 6s bane ane ee eee . 319 
7. Bhe- third branchialsnernveseeeeeneoies «sic. 4 = ce een Gee eee 320 
8) The truncussinbestino-accessorlusmxen.......)4< ceric eee 322 
Of The ramus recunrens SenslulvarseNeeeeee a)... ce eecieeneteiae a iene nee ee 324 
10) ‘he fourtheand snith branchialenenviess.4...65. sche eee eee eee 326 
1) he ramislateralessdorsalisnemeniiss..... 04. cee eee ene 328 
The firsteand secong: spinalanenviesteerseree tin... ae ae eee eee 330 
RSITEA0) 401-1 gh geraean yor mere tua Cetin MNS eA, 2.21 ey OO RRR Se SEER Eee Opes oe iden 332 
iteratunetcrted ics foo een ole oe elie boos nas occ acl re ee 336 
INTRODUCTION 
Fischer (1864) seems to be the first to give any accurate descrip- 
tion of the nervous system of Siren, for the account given by 
Vaillant (’63) is hardly worthy of mention. Fischer describes 
the seventh, ninth and tenth nerves, and gives some figures of 
the skeletal and muscular features of the head which show inci- 
dentally some of the minor nerve branches. In his description 
of the seventh nerve he overlooks the ramus mentalis externus, 
and confuses the ramus communicans vagi cum faciali with a 
‘‘Kopftheil des Sympathicus.’”’ Parker (’82) in his description 
of the skull of Siren, figures and mentions the exits from the skull 
of most of the main trunks of the cranial nerves. Wilder (’91) 
describes the nerves and muscles of Siren as shown by a general 
dissection of the head, although his analysis of the IX-X complex 
is far from satisfactory. Driiner’s account (’04) deals with the 
cranial nerves, only as they are related to the branchial muscula- 
ture. His descriptions are given with his characteristic clearness 
and with very few inaccuracies. Upon the subject of the nerve 
components in Siren previous writers have thrown little light. 
In the matter of nomenclature the writer has followed Fischer, 
Driiner and Osawa (’02) chiefly, attempting to avoid, as far as 
possible, on the one hand the formation of new names, and on the 
other the slavish subserviency of the systematist to priority. 
The BNA terminology must be applied with caution to amphib- 
ian structures until exact homologies are more satisfactorily 
determined. 
