1898.] HYOID OF AITTES OBSTETRICAlfS. 7 



hypobranchial cartilage which will ultimately develop iuto the 

 thyrohyal. 



There is not the same continuity of ceratobranchial and hypo- 

 branchial cartilage as is found ia. Pdoclytes ; such coalescence, in fact, 

 only occurs in the case of the fourth ceratobranchial. The third 

 ceratobranchial is attached to the postero-lateral edge of the hypo- 

 branchial cartilage by fibrous tissue, while opposite to the place 

 Avhere the second ceratobranchial should be attached is a small 

 foramen, the proximal end of the bar being kept in position only by 

 its connections with the first and third ceratobranchials. Cerato- 

 branchial 1 is attached by fibrous tissue to the lateral angle of the 

 hypobranchial plate at some distance outward from the posterior 

 ciisp of the ceratohyal ', and does not during later development 

 become fused with" it. There is thus an interesting difference 

 between the relations of the proximal end of ceratobranchial 1 in 

 Alytcs and Fehdt/tes, for while in the latter genus it is fused with 

 the hypobranchial cartilage and bound by connective tissue to the 

 proximal end of ceratobranchial 2 (9. p. 584), in Ahjtes it is 

 united with the hypobranchial by connective tissue and is fused 

 with the end of the second ceratobranchial. The difference is 

 important as well as interesting, inasmuch as the basal portion of 

 the first ceratobrancliial of Pelodijtes can be clearly seen to persist 

 as the postero-lateral process of the adult hyoid, while in Ahjtes the 

 whole of the first ceratobranchial becomes absorbed, and the 

 process of the hypobranchial cartilage to \\hich it was attached 

 broadens out into a plate from the edge of which the postero- 

 lateral process {pi>l) subsequently grows out (see figs. 5-7). 



Stage 2. Specimeu measurlmj 21 mm. from snout to root of tail. 

 LatKjtli of tail 4-1 mm. Length of hind limh, eMended, 19 mm. 

 Fore Umb>< extruded and measuring 8 mm. when extended. (Plate II. 

 fig. 2.) 



Although at this stage the tadpoles have four well-formed legs, 

 and have shed their horny jaMs, but slight changes have occurred 

 in the hyobranchial skeleton. The ceratohyals are larger and 

 slope a little more posteriorly than in the first stage. The front 

 copula is still present, but is smaller in proportion to the adjacent 

 parts. The width across the hyoid region is now equal to the 

 width across the branchial, whereas in the first stage it was less. 

 The first ceratobranchial exhibits a wrinkling at its distalend, the 

 absorption of cartilage having already begun in this position ; and 

 the laryngeal sinus is larger than before. 



1 Herein probably lies the explanation of tJie view propounded by Gaupp in 

 his paper on Sana (3. p. 403), that the part of the first branchial arch between 

 the spiculum and the hypobranchial plate belongs to the latter cartilage rather 

 than to the ceratobranchial. There is no indication of any separation of the 

 cartilages in Sana tadpoles, but as this author had, judging by his remarks on 

 page 411 of his treatise, already made an examination of the larval hyobranchial 

 skeleton of Alytes, it is just possible that his determination was influenced by 

 the division which in this genus occurs in the position in question. The 

 division is no more present in Pelodytes than in Sana, whence my hesitatiou 

 (9. p. 584, footnote 2) to accept Gaupp's theory. 



