974 MRS. O. A. MERRITT IIAWKES OX THE [DeC. 11, 



that canal, then this ramus in Chlamydoselachus is equivalent 

 to the true ramus oticus jtJ^its a few more nerve-fibres. Tlie 

 r. oticvis does not supply all the sense-organs which occur in the 

 region of the canal anterior to the commissural canal, but appa- 

 rently two of these are supplied by a dorsal bi'anch of the Glosso- 

 pharyngeus and the remainder by a dorsal branch of the Yagus. 



The branches of the ramus buccalis are arranged approximately 

 in two groups : one group being associated with the maxillary 

 branches of the mandibularis V.,and the other with the branches 

 of the maxillaris "V. The branches not only supply the diffuse 

 group of ampulla? which occurs above the mouth, but also a gi'oup 

 which lies between the descending portion of the infra-orbital 

 canal and the spiracle. This group is not usually represented in 

 Elasmobranchs. It is noteworthy that each of the branches 

 supplies both ampulla? of Lorenzini and neuromasts. This fact, 

 and the difiuse condition of the buccalis branches seem to indicate 

 that the nerve under discussion is in a primitive condition. The 

 anastomoses, which are so conspicuous in dissecting the branches 

 of the buccalis, indicate the first step from a primal to the secon- 

 dary condition, such as is found in most Elasmobranchs, where 

 the single buccalis of this species is represented b}' two or three 

 main branches. There are similar anastomoses in that portion 

 of the external mandibularis A'^II. where it is at some distance 

 from the neuromasts supplied. The anastomoses in the case 

 both of the bviccalis and external mandibulai'is VII. indicate a 

 secondary simplification of the nerve-supply. 



(c) The truncus hyomandibidaris of the Facialis originates from 

 the medulla by two roots at the same level as the roots of V. and 

 YII. It passes at first into the large foramen common to the 

 whole trigemino-facial complex, then bends backward and passes 

 ■outward through its own foramen. The distal end of the cephalad 

 root, which is probably the external mandibular lateral line root, 

 is connected with the Gasserian ganglion by several small strands — 

 the rami communicantes (Plate LXYIII. fig. 2, R.C.) : posteriorly, 

 the complex hyomandibular ganglion is connected with the auditory 

 nerve by the pars intermedia (fig. 2, P.I.). General cutaneous 

 fibres enter the hyomandibular ganglion from the Gasserian 

 ganglion by the rami communicantes. About 5 mm. from the 

 brain. Just as they emerge from the chondrocranium, the hyo- 

 mandibular roots unite and swell into a large ganglion, bilobed 

 at its distal extremity. The cephalad portion — the geniculate 

 ganglion — gives rise to the pre- and post-trematic YII. rami 

 (fig. 1, Pr.F. & Pt.F.). The caudad portion, which is the smaller, 

 is the external mandibular ganglion — that is, the most caudad 

 lateralis ganglion of the Facialis. This ganglion gives rise to the 

 truncus hyomandibularis, which contains the lateralis components 

 which separate out as the rami externi ma.ndibulares, as well as 

 «ome components of a branchiomeric nerve. 



There may be, in a form as low as Chlaniydoselachi(,s, general 

 ■cutaneous fibres belonging properly to the Facialis root, as well as 



