2 3 ANURA CHAP. 



as ill the Ranidae 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 vertel)ra, but there are 

 a few interesting exceptions. Pdobatcs, Pipa, and Hymenochims 

 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 Bombinafor with its single sacral vertebra. 

 The morphologically oldest condition is normally represented by 

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



Flu. 4. — Dorsal view of the sacral or ninth vertebra (9), with the attaeluuent of the ilium, 

 of (1) Rana teinporaria, (2) Bufo vvlgaris, showing the whole coccyx and pelvis, (3) 

 I'elobates fuscvx, as examples of cylindrical and of dilated sacral diapophyses. 

 (Ahout nat. size.) <t. Acetabulum ; c, coccyx ; /, ilium ; z, anterior zygapophyses. 



case has l)een recorded by Boulenger of Bomhinator pachypus 

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

 lop-sided abnormalities have been described in Bomhinntor and 

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

 ilium witli the ninth vertebra. This shifting forwards of the 

 ilium to the extent of one metamere has been continued further 

 in Pi'pa, in which the sacrum is formed by the ninth and eighth 

 N'ertebrae, their diapophyses fusing on either side into extra broad 

 wing-like expansions. In old specimens of Pa.laeohatraclmsfritsclii 

 tlie 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. diluvianns the 



