192 PROF. T. H. HUXLEY ON MENOBRANCHTJS. [Mar. 17, 



closely adherent, into an otic process (o, Plate XXXI. fig. 4). The 

 posterior division of the seventh nerve (which answers to what is 

 commonly called the facial nerve, and may be termed the hyo-man- 

 dibular division of the seventh) runs directly in front of the auditory 

 capsule, and beneath the otic process of the suspensorium. The 

 anterior division (palatine or Vidian division) of the seventh, on the 

 contrary, passes directly forwards, close to the pedicle of the suspen- 

 sorium, parallel with the orbito- nasal, and below but external to it. 



Meckel's cartilage (Mck.) is very thick at its articular end, but 

 rapidly tapers off to a point beyond the coronoid enlargement, to 

 which the elevators of the jaw are attached. The termination of 

 Meckel's cartilage lies at a considerable distance from the symphysial 

 end of the ramus of the mandible (Plate XXIX. fig. 1 and Plate 

 XXXI. fig. 7). 



The hyoidean arch has already been well described and figured by 

 Fischer. It is entirely cartilaginous and fibrous. It consists (Plate 

 XXX. fig. 2) of a long and stout ceratohyal cartilage (C.A), and a 

 small hypohyal (H.h). The two hypohyals are united with one 

 another by fibrous tissue, which represents the basihyal. Fibrous 

 tissue connects the proximal half of the ceratohyal with the suspen- 

 sorium and with the otic region of the skull ; and a strong ligamen- 

 tous band, the hyo-suspensorial ligament (h.s.l, Plate XXIX. fig. 1), 

 passes from the ceratohyal, at about the junction of its middle and 

 upper thirds, to the middle of the posterior edge of the suspenso- 

 rium. From this point another strong fibrous bundle, the suspen- 

 sorio-stapedial\\gnment(s.s.l), is continued upwards and backwards 

 to the stapes. The hyo-maudibular branch of the seventh nerve 

 (VII.p) passes above this ligament to its distribution, just as it passes 

 above the columella auris in the Frog. 



Rather above the attachment of the hyo-suspensorial ligament, 

 another strong band of fibrous tissue arises from the ceratohyal, and, 

 passing down on the inner side of the former, is inserted into the 

 angle of the mandible. This may be termed the mandibulo-hyoid 

 ligament, and answers to the interopercular element of the osseous 

 fishes' skull (Plate XXIX. fig. 1 and Plate XXXI. fig. 7,m.h.l). 



The branchial apparatus is composed of two median pieces, the 

 first and second basibraiichials (Bb 1 , Bb 2 ) ; of which the former is 

 cartilaginous, pointed in front, where it is connected with the fibrous 

 representative of the basihyal, broad behind, where it unites with the 

 two ceratobranchials (Cb l ). 



The second basibranchial is the only portion of the branchial 

 apparatus which is ossified, and has been described above. 



The stout anterior ceratobranchials (C6 1 )* meet in the middle 

 line, between the first and second basibranchials. The broad, dorsal 

 end of each articulates with the correspondingly broad, ventral end of 

 the first epibranchial (Ep.b 1 ), which is curved, and tapers to a 

 point at its dorsal extremity. 



* Fischer (/. c. p. 19) considers that these represent the anterior and posterior 

 ceratobranchials coalesced ; but I see no evidence that such a process has taken 

 place. 



