1875.] and Development of the Bat?*achian Skull. 141 



Tor a longer period in the Urodela the suspensorium is quite separate 

 from the trabecula ; as a rule it soon forms three attachments ; but in 

 this group, as in the Anura, it never unites by confluence with the next 

 or hyoid arch. 



Each of these groups has its typical method of attaching the suspen- 

 sorium, and each has types that show remarkable modifications. 



In Menobranehus and Rana (Huxley, he. cit.) we have the two proper 

 types of this structure in the adult. 



In the former, the Sauro-batrachian, the apex of the mandibular arch 

 unites with the trabecula near its apex on its outside by a process, the 

 " pedicle," which lies beneath the trigeminal nerve. 



A second or " ascending " process mounts over part of that nerve, espe- 

 cially arching over the orbito-nasal and the Vidian branch of the facial nerve, 

 and it unites with the top of the alisphenoidal crest of the trabecula. 



A third, the " otic process," grows upwards and backwards, and unites 

 with the outside of the auditory capsule ; it is pedate, and its thick end 

 runs in front of the ampulla of the horizontal canal. 



In the typical adult Batrachian suspensorium the primary union of 

 the apex of the mandibular pier is afterwards lost, this part becoming 

 mere fibrous tissue ; but the lower part of the pedicle grows into a thick 

 triangular process of cartilage with its base upwards, and this base 

 becomes the "condyle of the pedicle;" it articulates with the side of the 

 auditory capsule antero-inferiorly. This condyle has its counterpart 

 in some of the Urodela as a swelling of the pedicle near the origin of the 

 otic process below (Huxley, " On Menobranehus" plate 29. fig. 2). 



In the adult frog the suspensorium is united by a gliding joint to the 

 auditory capsule below, and by fusion of cartilage above and behind. 



As far as my observations go, Siredon agrees with Menobranehus ; in 

 Salamandra the swelling answering to the " condyle of the pedicle" is 

 very small, and the pedicle is suppressed. In the lowest type also, namely 

 Proteus anguinus, the ascending process only is present, and the otic pro- 

 cess is small. Some of the Batrachia differ from the frog in having 

 the lower part of the " pedicle" greatly enlarged at first, but very small 

 afterwards, forming a very small condyloid part ; whilst the apex is not 

 absorbed, but unites with the auditory capsule. This is seen in Bufo 

 vulgaris. 



Moreover in that type and in Dactylethra, when the legs are well 

 developed, the otic process projects inwards in front of the auditory cap- 

 sule. In Pseudis paradoxa this is very distinct as a thick, finger-shaped, 

 free process, which passes inwards as far as the neck of the foremost 

 ampulla. 



The last is an instructive condition, as it partly breaks down the fence 

 between the two groups of Amphibia ; for in the Urodela the otic process 

 is pedate, the toe projecting to nearly the same extent inwards as in 

 Pseudis. The term " suspensorium " must not be applied to the part 



