LINiVKAN SOCJETT OF LONDON. 89 



centra. Whether this is an invariable condition in tliat genus 

 or whether the description was based upon the examination 

 of a variable individual, 1 have no means of deciding, but the only 

 member of this family (or sub-family) which 1 have examined, 

 a specimen of Ctratohijla huUtlus, was certainly uniformly pro- 

 ctelous. In the former case the genus would appear to furnish 

 a link between the Proccela and the Opisthoctela comparable 

 to that supplied by Megaloplirys between the Opisthoccela and 

 the Auomoccela. 



Apart, however, from this single, possibly excei)tional, genus, 

 there has been described but a single instance of the occurrence 

 of variable centra in these three great families which comprise 

 the majority of living Anura *. 



Jlemarking upon the resemblance which exists between many 

 of the Cjstignathidse and the Hanidte, Gadow says ('oi, p. 210), 

 "young Eanida3, before the firmisternial character is assumed, are 

 indistinguishable from the Cystignathida?, and the latter would 

 turn into lianidie if they could be induced to consolidate their 

 sternal apparatus," The condition of the vertebral centra, how- 

 ever, permits of a distinction being readily nuide even between 

 these innnature forms. 



(iv.) The Diplasiocoilous condition (which, as already pointed 

 out, is I'estricted to Firmisternial forms) is likewise extreniely 

 constant, individual variations being almost unknown. The 

 occurrence, therefore, of two or three genei'a at present included 

 in the Firmisternia, in which the diplasioccelous condition has, 

 apparently, not been attained, is a matter of considerable 

 interest. 



Thus, among the Engystomatida; which, as Gadow points out 

 {op. cit. p. 143), may be connecting links between the Proco?la 

 and Diplasiocoela, I hud three s[)ecimens exhibiting the uniformly 

 proctelous condition. Tuese are one example each of Atelojrus 

 o.vifrJii/ncJius, A. ignescens, and liJiombophrifne testudo. Having had 

 but a single skeleton of each of these three species for examina- 

 tion, I am unable to say whether or no these are cases of individual 

 variation, it is scarcely probable, ho\^ever, that two specimens 

 belonging to distinct species should both have chanced to be 

 similarly abnormal, and it may be assumed that Afelojms is 

 normally proccelous. It is not, however, surprising that we 

 sliould find in one or two genera which have become firmisternial, 

 that there is a retention of what must be recognized as a more 

 primitive condition of the vertebral column. 



A more puzzling exception is met with in the genus lUiaco- 

 phorus, and there can be, 1 think, in this case, no question of 

 abnormality or individual variation. 



The genus is one in which Eoulenger has merged the genus 

 I'olypedates, and it is represented, in the British Museum collec- 

 tion of skeletons, by nine specimens. Of these, four, belonging to 

 the species li. mucuhitus, li. cruciger, 11. macrotls, aiul li. robi(sh(s, 



* The specimen of Ldrbcrora-^cs tlescribed liv Cdjie ('66). 



