22 



ANURA 



CHAP. 



as in the Eanidae and Cystignathidae, or they are more or less 

 dilated as in all the other families, most strongly in the 

 Pelobatidae and the Aglossa. In some members of the large 

 sub -family of the Cystignathidae the otherwise cylindrical 

 diapophyses are slightly dilated. 



The sacrum is formed by the ninth vertebra, but there are 

 a few interesting exceptions. Pelobates, Pipa, and Hymenochirus 

 possess two sacral vertebrae ; and, neglecting individual abnor- 

 malities, these three genera form the only exception amongst 

 recent Amphibia. In the three genera the coccyx is fused with 

 the second sacral vertebra, and such a fusion occurs elsewhere 

 normally only in Bombinator with its single sacral vertebra. 

 The morphologically oldest condition is normally represented by 

 Pelobates, the sacral vertebrae being the tenth and ninth. One 



FIG. <!. Dorsal view of the sacral or ninth vertebra (9), with the attachment of the ilium, 

 of (1) Rana temporaries, (2) Bufo vulgaris, showing the whole coccyx and pelvis, (3) 

 Pelobates fuscus, as examples of cylindrical and of dilated sacral diapophyses. 

 (About nat. size.) a, Acetabulum ; c, coccyx ; i, ilium ; z, anterior zygapophyses. 



case has been recorded by Boulenger of Bombinator pacliypus 

 " with eleven segments," the last carrying the ilium. Individual 

 lop-sided abnormalities have been described in Bombinator and 

 Alytes, where the right ilium articulated with the tenth, the left 

 ilium with the ninth vertebra. This shifting forwards of the 

 ilium to the extent of one metamere has been continued further 

 in Pipa, in which the sacrum is formed by the ninth and eighth 

 vertebrae, their diapophyses fusing on either side into extra broad 

 wing-like expansions. In old specimens of Palaeobatraclmsfritschi 

 the seventh vertebra is in a transitional condition, the ilium 

 being carried by the ninth and eighth, and slightly also by the 

 diapophyses of the seventh vertebra ; and in P. diluvianus the 



