SKELETOlSr AND LAETNX OE SEISTOPUS AND PIPA. 101 



resemble in shape the arytenoids of most Anura (cf. Bomhinator, 

 fig. 13), aud differ in a marked degree from the arytenoids of the 

 adult. They are closely applied to one another in the median 

 line, as in the typical Anuran larynx, and not as in the adult 

 Xenopus. The cricoid is an annular cartilage, more extensive on 

 the ventral than the dorsal surface, and quite free from thethyro- 

 hyals. The ventral portion terminates anteriorly in a blunt 

 point a short distance behind the anterior ends of the arytenoids, 

 and is produced behind into a pair of narrow bands (fig. 10, Ir.) 

 which support the ventro-internal walls of the bronchial tubes. 

 This early appearance of the bronchial cartilages is well worthy 

 of note. The roof of the larynx is expanded in front, and the 

 dorso-lateral corners are produced into a pair of blunt processes 

 which are doubtless to be identified with the blinker-shaped 

 processes of the adult (PI. 8. fig. 3, bl.). The posterior edge of 

 the roof is concave. The sides of the cricoid do not extend 

 forward, so that the whole of the arytenoid can be seen in a side 

 view. 



Parker neither discusses nor figures the branchial skeleton of 

 his youngest Xenopus larva — first stage, with no traces of paired 

 limbs, total length Ij inch — but the figure he gives (33. PI. 56. 

 fig. 6) of the hyoid arch and mandible of this stage corresponds 

 almost exactly with that of my Stage I. The broadened posterior 

 extremity of the basihyal he regards as the first basibranchial, 

 but beyond that we do not diff"er. Parker's second stage — tad- 

 pole, If inch long — of the limbs of which we have no means of 

 judging, would also appear to correspond with my first stage ; for 

 in his side view of the hyobranchial skeleton (which, curiously 

 enough, he draws upside down), the branchial cartilage is still 

 considerably inflated and fits up closely behind the ceratohyal. 

 He is silent concerning the hyobranchial skeleton of his third 

 stage, — tadpoles at their largest size — ; but in his fourth stage — 

 young, with large legs and diminishing tail — which, judging from 

 the second qualification, should be older than my Stage III., he 

 figures (33. PI. 58. fig. 4) the two ceratohyals as still distinct, 

 and the basihyal as still recognizable. The cartilage, which in 

 this figure he indicates by outline only and marks Ir. 1, is, I am 

 convinced, the whole of the hypobranchial plate, shown in my 

 fig. 3 at M. 



