CRANIAL NERVES OF SIREN LACERTINA g20 
laryngeus muscle (dl.1) may arise from the intestino-accessorius 
farther anteriorly than the one above mentioned, or it may spring 
from the ramus sensitivus recurrens to be described later. From 
the intestino-accessorius near where it begins to curve dorsally 
there may arise a pharyngeal branch (figs. 42-44, ph.i-a.) of com- 
munis fibers which supplies the dorsal pharynx wall posterior and 
medial to the third and fourth branchial arches. . 
The three main divisions of the truncus intestino-accessorius 
are: (1) The ramus lateralis ventralis (Jat.V), of lateral line fibers, 
which passes antero-ventrally and then posteriorly to innervate 
the ventral series of neuromasts of the trunk. (2) The ramus 
intestinalis (¢nt.) of communis fibers, which, after division into 
two branches, passes postero-ventrally into the visceral region. 
(3) The ramus intestinalis recurrens, (int.rec.), in Siren exclu- 
sively motor, which runs antero-ventrally into the ventral branch- 
ial and laryngeal region. It divides into three branches, one 
supplying the subarcualis rectus and subarcualis obliquus 2 mus- 
cles (sar. + sao.2), a second innervating the interbranchialis 
4 muscle (7b.4) and the third branch, which may be termed the 
laryngeus recurrens (lar.rec.), after passing along the medial 
border of the laryngeal portion of the dorso-laryngeal muscle, 
supplies the laryngeal muscles: laryngo-trachealis ventralis, laryn- 
geus ventralis, laryngeus dorsalis, and constrictor laryngeus. 
Fischer describes and figures in Siren two branches of the laryn- 
geus recurrens as passing across the middle line and forming two 
loops out of which no fibers pass. Driiner mentions a commis- 
sure between the two laryngeus recurrens nerves. The writer finds 
the two branches mentioned by Fischer. The posterior one unites 
in the middle line with the one from the other side, forming a 
nerve which, running anteriorly in the middle line between the 
two laryngo-trachealis ventralis muscles, is distributed to the lat- 
ter. The anterior branch apparently passes in a commissure 
wholly across the middle line to the muscle of the opposite side. 
Wilder describes and figures (1. ¢., p. 670) the interbranchialis 4 
(hyotrachealis) muscle as innervated ‘‘by a recurrens nerve which 
branches from one of the vagus twigs supplying the external gills.”’ 
As the intestino-recurrens nerve is leaving the other elements of 
