138 Mr. W. K. Parker on the Structure [Dec. 16, 



with the auditory capsule : newer and more correct names of the attaching 

 processes of the " suspensorium " are here given, in accordance with the 

 nomenclature adopted by Professor Huxley in his memoir on Meno- 

 branchus (Proc. Zool. Soc. 1874, p. 186). 



For instance, the band which connects the mandibular arch primarily 

 with the trabecular is now called the " pedicle," and the secondary pro- 

 cess which binds on the ear-sac is the "otic process." There is no 

 " ascending process " over the orbito-nasal nerve, as in the salamandrian 

 forms ; and the apex of the pedicle losing its distinctness, its lower part 

 forms a condyle which articulates with the outer face of the auditory 

 mass below. 



The apparent distinctness of this part in the young frog kept up the 

 illusion as to its being a part borrowed from the next arch. It was called 

 by me the " infra-hyomandibular." 



The cartilage which I erroneously supposed to be the rudiment of the 

 " columella " lies over the portio dura nerve ; it was called by me the 

 " supra-hyomandibular." It is in reality the rudiment of the cartilagi- 

 nous ear-ring. 



All this, thanks largely to my friend and fellow worker, is made 

 plain now. 



In frogs it is not quite easy to recognize the supero-anterior element 

 of the double hyoid arch of osseous fishes in the columella ; in toads it is 

 easier. 



In the frog a small cartilaginous segment is cut off from the proximal 

 end of the shaft of the columella, and lies between it and the stapes. In 

 toads the proximal element is the longer of the two, and is distinguished 

 by being ossified separately, and not by subdivision of the cartilage. 



Hence it is not a wild supposition that the proximal shaft-bone may 

 be the " hyomandibular " and the distal the " symplectic," its unossified 

 end being dilated as the " extrastapedial." 



In osseous fishes we have this supero-anterior bar in the hyoid region 

 ossified by two centres, but no stapes ; in the Urodela the stapes, 

 but, as a rule, no supero-anterior bar ; in toads we have both, whilst in 

 frogs the apex of the upper pier is a free nucleus of cartilage. 



The primordial cartilaginous skull of the common toad is here worked 

 out, the subjects being tadpoles only one third of an inch in leugth ; 

 their black colour and granular texture made them most difficult ob- 

 jects to interpret, and cost me much anxious labour. 



Then in a series of stages comparable with those of the common frog 

 I have traced the metamorphosis of the facial arches, so that the skull of 

 the two common kinds of Batrachia will now be intelligible. 



In the tadpole of Daetylethra there is much that is new and strange ; 

 there are neither suctorial mouth nor horny jaws. The upper labial 

 forms the edge of a broad mouth with an underhung lower jaw, the 

 head being extremely depressed, as in certain siluroids and in the frog- 

 fish (Lophius). 



