1897.] SKELETON OF PELODYTES PTTNCTATUS. 581 



half-grown specimens the cartilage bounding the foramen postero- 

 externally is very thin and readily tears away, giving the impression 

 that there exists here an unenclosed sinus such as is shown bv 

 Duges (4. pi. 3. fig. 18) and Parker (12. pi. 25. fig. 9). Both 

 Duges and Parker fail to depict the hyoid arch correctly. The 

 liberated part of the cornu (A', 7t", fig. 12) resembles very closely 

 in size and shape that of Pelodytes. It is lamellar in front, and 

 ends behind in a hooked process attached to the skidl. Parker 

 errs by representing it as rod-like and not separated from the rest 

 of the arch, while Duges fails to notice it at all in pi. 3. fig. 18, 

 but shows it as a rod-like cartilage in pi. 13. fig. 79. Parker (12. 

 p. 261) says that there are two small centres of ossification on 

 each side in the anterior cornua of Pelohates, but this statement I 

 cannot confirm. Cope's figure (2. pi. 76. fig. 5) of the hyoid of 

 Pelohates is not original, but is admitted to be based on the figures 

 of Duges and Parker. The thyrohyals of Pelohates are massive, 

 more especially in old specimens ; and the epiphysis is produced 

 laterally beyond the outer edge of the shaft, giving to the 

 thyrohyal a hooked appearance. 



There is no ventral ossification such as occurs in Pelodytes. But 

 whether this fact points to a closer alliance between Pelodytes and 

 Alytes than between Pelodytes and Pelohates is, I take it, very 

 doubtful. The bones, in the first place, are not ossifications of 

 the hyobranchial skeleton, but ossifications applied to the surface 

 of it at a late stage of development. If we compare the adult 

 hyoids of Pelohates, Pelodytes, and Alytes we find that the two 

 former resemble one another and differ from the third in the 

 disjointing of the byoidean cornua, the presence of lateral foramina, 

 and the partial enclosui-e of the hyoglossal sinus ; while the two 

 latter resemble one another and differ from the first only in the 

 presence of the ventral splint-bone. Also, if we compare the 

 larval hyobranchial skeleton of the three, we find that in Alytes 

 the basihyal extends so far back as to completely separate the 

 hypobranchial plates from one another, whereas in both Pelodytes 

 and Pelohates the two hypobranchial plates are in contact in the 

 median line for some distance behind the basihyal. And in Alytes 

 there is a well-marked median plate of cartilage (the "erste Copula" 

 of Gaupp, 5. p. 412) situated in front of the opaque fibrous band 

 connecting the ceratohyals ; but I find no trace of this in larvae 

 of Pelohates and Pelodytes. And these latter are fundamental 

 differences appearing early, and of an importance which it would 

 be difficult to exaggerate. 



Development of the Hyohranchial Skeleton of 

 Pelodytes punctatus. 



The method employed in the investigation of the larval hyo- 

 branchial skeleton was of the simplest character. The tadpoles 

 were dissected under spirit, the mandible and hyoid arch disarti- 

 culated from the palatoquadrate cartilage, and the branchial skeleton 



