372 ON THE SACRAL VERTEBRiE OE LTZARDS. . 



presacral nerve. But Monitor and Ohamcsleo present a slight ex- 

 ception in certain respects. 



In all the Eeptilia examined and enumerated bj the authors, 

 the transverse processes which atrnt against the ilium are wholly 

 or in part parapophysial, and are in serial relation (serial homo- 

 logues) with the capitular processes (or the capitular parts of the 

 transverse processes) of the more preaxial vertebrae. The junction 

 of the sacral vertebrae with the ilium is much postacetabular in 

 Saurians ; but in Crocodilia and Tortoises (some at least) it is about 

 opposite the acetabulum. 



In Batrachians the transverse processes abutting against the 

 ilium are parapophysial, but diapophysial in nature like those of 

 Reptiles. 



In Mammals as compared with Lizards, it would seem, with 

 respect to nerves, that the first and second sacral vertebrae (say, for 

 instance, of the Cat), answer very well to the two vertebrae with 

 enlarged transverse processes of Lizards, while osteologically they 

 of course also auswer very well to them. There can be little 

 doubt, however, that the first two sacral vertebrae of the Cat 

 are to be considered homologous with the anterior human sacral 

 vertebrae; and therefore it would seem that the twoilium-joiniug 

 vertebrse of Lizards should be considered homologous with the 

 anterior human sacral vertebrae. 



In Man, the Cat, and also in other Mammals down to the 

 Echidna, the transverse processes abutting against the ilium are 

 parapophysial, like those of Reptiles and Batrachians. In all the 

 Mammals examined by the authors, however, the junction of the 

 sacral transverse processes with the ilia is preacetabular, although 

 that junction is much less preacetabular in position in Man than 

 it is in most Mammals. 



Altogether, from the osseous and nervous conditions evinced 

 together in the groups hitherto referred to, the authors propose 

 the following definition of a "Sacral Vertebra" in Mammals, 

 Reptiles, and Batrachians : — " vertelra with parapophysial trans- 

 verse processes which aiut against the ilium, preaxial or post- 

 axial or opposite to the acefalulv/m, and having a root of the sciatic 

 plexus coming forth either immediately preaxiad or postaxiad of it. " 



This definition will exclude from the sacrum, as not abutting 

 against the ilium, of Man, the more posterior vertebrae called 

 "sacral "in anthropotomy. But in the lower mammals (even 

 already in Apes) the number of so-called " sacral " vertebrae aug- 



