HYNOBIIDAE. 449 



Larval Onychodactylus have a fold of skin along the hind border of 

 the limbs as do the Cryptobranchidae. 



According to Noble (Bull. Amer. Mus. Nat. Hist., XLVI, 1, pp. 

 1-87, 1922) the Cryptobranchidae differ from other salamanders in 

 having the pubotibialis muscle fused with the puboischiotibialis, and 

 in having the iliotibialis not in contact with the ilioextensorius. My 

 own dissections of H. leechii and of 0. japonicus show agreement with 

 the Cryptobranchidae in that they too have the pubotibialis fused with 

 the puboischiotibialis, but in the other character they agree with the 

 majority of salamanders and the two'muscles in question are in con- 

 tact nearly throughout their length. Dr. Noble holds that the Crypto- 

 branchidae are primitive in having these muscles separated, but I 

 think this view untenable, as they are in contact in Hynobius and in 

 Onychodactylus, and I would suggest that their separation in Crypto- 

 branchidae is a consequence of the dorso-ventral flattening which 

 these animals have undergone, the flattening and widening of the 

 thigh having drawn these muscles somewhat apart. 



I find the following elements in the carpus of H. leechii: radiale, 

 ulnare (to which is fused the intermedium), two centralia, four car- 

 palia, and a bit of cartilage corresponding to the tubercle under the 

 base of the first finger which according to Kehrer is a rudiment of the 

 prepollex. In the tarsus I find tibiale, intermedium, fibulare, two 

 centralia, six tarsalia and a bit of cartilage corresponding to the 

 tubercle under the base of the first toe. These small bits of cartilage 

 are distal to and in line with the radiale and first carpale and the 

 tibiale and first tarsale respectively. All the other elements as well 

 as the digits converge strongly towards the ulnar or the fibular. This 

 state of affairs is quite in consonance with the findings of Wiedersheim, 

 Kehrer, and Schmalhausen, in //. keyserlingii and in Ranodon. Their 

 conclusions were that the original Tetrapod appendage was hepta- 

 dactylous, and that these Asiatic salamanders had the most primitive 

 carpus and tarsus found in living Tetrapods. The tubercles at the 

 bases of the first digits are of almost universal occurrence in Hyno- 

 biids, and Kehrer's idea that they represent prepollex and prehallux 

 is worthy of consideration. 



The fifth toe is lacking in Batrachuperus, in H. keyserlingii, and in 

 H. cristatus. It is nearly always absent in H. kimurai, and may occa- 

 sionally be missing or rudimentary in other species of Hynobius. 



Batrachuperus and Pachypalaminus have the under surfaces of the 

 hands and feet and the tips of the digits covered with thickened, 

 horny epidermis. 



