352 H. W. NORRIS AND SALLY P. HUGHES 



which are interpreted as somatic sensory. It may be suggested 

 that microscopical examination will show that these supposed 

 general cutaneous nerves end in pit-organs or similar structures, 

 as in Squalus. 



Cole ('96) describes in Chimaera "two groups of ampullae, 

 situated behind the lower jaw," and innervated by the ramus 

 mandibularis externus. These ampullae are small and simple 

 in structure, and probably correspond to the small rudimentary 

 ampullae and the near-by larger tubular organ in Squalus, inner- 

 vated by branches of the ramus mandibularis externus VII. 



The ramus mandibularis internus VII. Slightly posterior and 

 dorsal to the origin of the anterior division of the ramus man- 

 dibularis externus from the hyomandibular trunk the ramus 

 mandibularis internus is given off (figs. 48 and 51), and as the 

 visceral sensory terminal branch of the hyomandibular trunk 

 passes transversely around the lateral edge of the hyoid cartil- 

 age, into the interval between the latter and Meckel's cartilage, 

 and turning anteriorly runs along the dorsomesial border of the 

 latter between it and the hyoid cartilage, as far as the anterior 

 end of the latter. Thence it continues anteriorly between the 

 ventrolateral edge of the basihyal and Meckel's cartilage, now 

 dividing into a number of small branches. Its area of distribu- 

 tion is the lower jaw and the ventrolateral floor of the mouth 

 mesial and anterior to the chorda tympani. 



The ramus hyoideus VII. As the hyomandibular trunk 

 passes along the lateral border of the second dorsal constrictor 

 muscle, it gives off numerous small twigs to the muscle (fig. 49). 

 Farther ventrally the remaining motor fibers separate from the 

 lateral-line elements, which form the posterior branch of the 

 ramus mandibularis externus, at the lateral border of the hyoid 

 cartilage, as described above. Thence as a compact nerve they 

 pass ventrally around the hyoid cartilage to the ventral side of 

 the lower jaw, and turning anteriorly between the first and sec- 

 ond ventral constrictor muscles are distributed to the second 

 ventral constrictor and the posterior part of the first constrictor. 



