270 



PfiOF. G. B, 



nOWES OX THE DEVELOPilEXT OF THE [^Lar. 14, 



and certain other genera, and the more regular if not diagnostic 

 ankylosis of the first two vertebrae of the living Pipa, Xenopm, 

 Pelohates\ and others, and of the extinct PaheoU(trachus'\ The 

 fact that Ceratophnjs and Pehhates, in which this tendency towards 

 a greater fusion is well marked, are possessed of a relatively short 



So-called atlas of Baiia and Siredon. 



Fig. 3. The so-called atlas of i?anarrt<zoro<Zo«, exceptional. Fig. 4. The so-called 

 &t\a.6oi Hana escidenta : a, normal; h, exceptional. Fig. 5. The same in 

 Eana cate-ihiana : a, normal ; h, exceptional. Fig. 6. The same in 

 the Mexican Asolotl, Siredon pisciformis. All from the ventral aspect. 

 Figs. 3, 4, and 6 enlarged. 



«, nerve-aperture for exit of trans-atlantal nerve ; tr, transverse pro- 

 cess; X, eminence at point of fusion of adjacent vertebral bodies. 



urostyle, invests the aforenamed anticipation with an amount of 

 interest, by way of suggesting that the reduction in length of 

 the urostyle and the vertebral ankylosis may be associated modi- 

 fications. 



In the majority of Anuran skeletons that I have examined, in 

 which co-ossification of adjacent vertebrae had been effected, all 

 traces of their original lines of demarcation were lost on the venti'al 

 surface, the centra passing insensibly into one another. In the 

 Frog first described this was otherwise, for its vertebral column 

 wlien newed from beneath (fig. 1 a) or from the side (fig. 1 c), 

 revealed a couple of eminences (a-) at the point of fusion of the 

 two terminal vertebrae. 



There is no variation to which the Amphibian vertebral column 



1 Cf. Hoffmann, in Bronn's Klassen und Ordnung. d. Thier-Reichs, " Amphi- 

 bien," (Ed. vi.) p. .57. 



^ Cf. Walterstorff, op. cif,, and Adolphi, loc. cit. p. 362. I have observed 

 a similar fusion of the first two vertebrae in individuals of Eana guppyi and 

 R. catesbiana. 



