326 



this diverticulum the Gasserian recess, and it is too evidently the 

 homologue of the membranous trigemino-facialis chamber of Bdello- 

 stoma to need comment of any kind. The maxillo-mandibularis and 

 lateralis nerves of the fish are said by Bridge to issue from thi& 

 recess into the so-called "Schläfengrube", and to traverse that "Grube" 

 to reach the outer surface of the suspensorial' cartilage. The hyo- 

 mandibularis facialis issues into the same "Grube", and, through it,, 

 reaches the inner surface of the suspensorial cartilage; the "Grube'* 

 perforating the cartilage. As the trigeminus and facialis nerves issue 

 from the cranium they are separated from each other by a bar of 

 cartilage that forms part of the side wall of the Gasserian recess. 



Comparing Bdellostoma with Amia and Lepidosiren, it at once 

 suggests itself that the cartilage that forms the lateral boundary of 

 the maxillo-mandibularis and facialis foramina of the former must be 

 represented, in the two latter, in a part of the skull. This is con- 

 firmed by comparison with certain of the Amphibia. 



In Menobranchus, Huxley (12) says that the suspensorial car- 

 tilage has an otic and an ascending process, the latter of which 

 "applies itself to the outer side of the trabecular cartilage". He 

 further says that "The ganglia of the trigeminal and of the seventh 

 nerves are situated close together, above the trabecula, where it 

 passes into the floor of the auditory capsule" ; and that "Immediately 

 in front of these ganglia, the trabecula is produced externally, and 

 becomes continuous with the Suspensorium by the process (m), which 

 thus affords the middle and chief attachment of the Suspensorium ta 

 the skull, and may be named the pedicle of the Suspensorium". The 

 trigeminus and facialis are said to issue from the skull by a single 

 large foramen; the ganglia of these nerves lying outside this foramen 

 and hence outside the cartilaginous skull. The ramus ophthalmicus 

 trigemini is said to run forward ventral and internal to the ascending 

 process, and hence along its anterior side; the truncus maxillo-man- 

 dibularis running outward, dorsal and external to the same process,, 

 and hence along its posterior side. Huxley then says that because 

 of this "it looks as if the process . . . divided the foramen of exit 

 of the trigeminal nerve into two parts". This would seem to imply 

 that, in his opinion, the process might be, or might become, a part of 

 the skull. The palatine branch of the facialis is shown running for- 

 ward, apparently across the dorsal surface of the pedicle and then 

 downward through a large opening that lies between the pedicle be- 

 hind and the ascending process in front ; the nerve thus lying anterior 

 to the one, and posterior to the other. It passes external to the 



