480 AN ABNOEMLili TERTEBRAL COLIJMIf OF THE BULL-EEOG. [June 5, 



This piece, taken by itself, as we have seen, shows very little 

 asymmetry — it is quite similar to the Python's vertebra figured by 

 Bateson, and his description (p. 105) and explanation \\ould 

 equally apply here. But we see that, in the Frog, no asymmetry 

 of tlie entire column results. It would, no doubt, be too 

 laborious to count the entii'e number of ribs in a Python, but the 

 suggestion may be made that the apparent " partial division "' on 

 one side (fig. 10, II., of Bateson) may be due to the same cause as 

 I suggest above, and that it might be " rectified " further back by 

 another half on the opposite side. He mentions, however, that 

 the ISotli vertebra of this same Python " had a similar doubling 

 of the right side," so that, no doubt, he would have observed any 

 corresponding doubling on the left side if it had existed. 



In bis paper on abnormal Progs' vertebrae, just mentioned, 

 Howes refers to the rarity of the " fusion " of the eighth aud 

 ninth in R. escidenta, so that it seems worth while to add to his 

 specimens two others which I have met with ; whereas Adolphi ^ 

 found only one such case in 212 Toads examined, I have met with 

 two cases in eight skeletons of R. mugiens (exclusive of the 

 abnormal specimen just described). In each of these two 

 skeletons, in fact, the conditions of the sacral and eighth vertebras 

 are precisely those described and figured by Howes on p. 269 

 (figs. 1 a, 1 S, 1 c), and, as there, my specimens present the slight 

 ridge at the line of fusion. It seems, then, that B. mugiens pre- 

 sents great scope for Mr. Bateson : various kinds of " variations " 

 occurring evidently with considerable frequenc_y. 



Having met with these instances, it seemed desirable to look 

 over the skeletons in our Museum, so as to note any other 

 abnormalities in the vertebral column which might be presented 

 by them. I was rewarded by finding two cases in species of 

 Toads. The first case occurs in a dried skeleton of Bufo agua, in 

 which the " atlas " is co-ossified with the second vertebra. 



The second and more remarkable case I noted in B. jjantlierinus. 

 Here the seven anterior vertebrae are perfectly normal, but the 

 eighth and ninth are united with one another, and the latter with 

 the urostyle (see fig. 16, uat. size). The transverse process of the 

 eighth is fairly stout, that of the ninth is, as usually the case in the 

 genus Bufo, very considerably expanded ; whereas the union of the 

 eighth and ninth centra is indicated by " Howes' ridge," there is 

 no indication of the junction between ninth aud the urostyle, the 

 centrum is here quite smooth. The sacral transverse process is 

 continuous with the lateral flange or ridge of the urostyle, and 

 there is no " coccygeal foramen " for the tenth spinal nerve, such 

 as usually occurs, the last perforation being just behind the 

 enlarged transverse process. 



Similar instances of fusion of the ninth vertebra with the urostyle 



1 Adolphi, Morph. Jahrb. xix. p. 320. 



