DEVELOPMENT OF ELASMOBRANCH FISHES. .195 



The second division of the fifth nerve is the superior maxillary, 

 which appears to me to arise from both the first and second roots of 

 the fifth, though mainly from the first. It divides once into two 

 main branches. The first of these — the buccal nerve of Stannius — 

 after passing forwards along the base of the orbit takes its course 

 obliquely across the palatine arch and behind and below the nasal 

 sack, supplying by the way numerous mucous canals, and dividing at 

 last into two branches, one of these passing directly forwards on the 

 ventral surface of the snout, and the second keeping along the front 

 border of the mouth. The second division of the superior maxillary 

 nerve (superior maxillary of Stannius), after giving ofi" a small 

 branch, which passes backwards in company with a branch from the 

 inferior maxillary nerve to the levator maxillae superioris, itself 

 keeps close to the buccal nerve, and eventually divides into numerous 

 fine twigs to the mucous canals of the skin at the posterior region of 

 the upper jaw. It anastomoses with the buccal nerve. The inferior 

 maxillary nerve arises mainly from the second root of the fifth. After 

 sending a small branch to the levator maxillae superioris, it passes 

 outwards along the line separating the musculus adductor man- 

 dibulse from the musculus levator labii superioris, and after giving 

 branches to these muscles takes a course forward along the border of 

 the lower jaw. It appears to be a mixed motor and sensoiy nerve. 



The seventh or facial nerve arises by a root close to, but behind 

 and below the second root of the fifth, and is intimately fused with this. 

 It divides almost at once into a small anterior branch and large 

 posterior. 



The anterior branch is the palatine nerve. It gives ofi" at first 

 one or two very small twigs, which pursue a course towards the 

 spiracle, and probably represent the spiracular nerves of other Elas- 

 mobranchs. Immediately after giving off these branches it divides 

 into two stems, a posterior smaller and an anterior larger one. The 

 former eventually takes a course which tends towards the angle of 

 the jaw, and is distributed to the mucous membrane of the roof 

 of the mouth, while the larger one bends forwards and supplies the 

 mucous membrane at the edge of the upper jaw. The main stem of 

 the seventh, after giving off a branch to the dorsal section of the 

 musculus constrictor superficialis, passes outwards to the junction of 

 the upper and lower jaws, where it divides into two branches, an 

 anterior superficial branch, which runs immediately below the skin 

 on the surface of the lower jaw, and a second branch, which takes a 

 deep course along the posterior border of the lower jaw, between it 

 and the hyoid, and sends a series of branches backwards to the ven* 

 tral section of the musculus constrictor superficialis. The main stem 

 of the facial is mixed motor and sensory. I have not noticed a 

 dorsal branch, similar to that described by Jackson and Clarke. 



The auditory nerve arises immediately behind the seventh, but 

 requii'es no special notice here. A short way behind the auditory is 

 situated the root of the glossopharyngeal nerve. This nerve takes an 

 oblique course backwards through the skull, and gives off in its pas- 



