1879.] Cliaracters of the Pelvis in the Mammalia, $r. 



403 



and the posterior halves of the rami are closely adherent to the fascia 

 of the external oblique in the middle line, and lie between the inner 

 edges of the two recti. Finally, the fibres of the transversus (fig. 13, Trs.) 

 are inserted into the outer edges of the rami, and the fascia which 

 unites these appears to belong to the transversus. 



On comparing the recti and the muscles A, B, C, with those of Or- 

 nithorhynchus and Echidna, a great apparent difference manifests itself. 

 For the very thin recti of the Monotremes take their origin from the 

 pubis along a line which extends from the tubercle to close to the 

 symphysis, and pass forwards, dorsad of the marsupial bones and the 

 pyramidales, which thus lie altogether in front of them and are, by 

 them, largely separated from the fascia trans versalis. Nevertheless, 

 it will be observed that the origin of the muscle B nearly corre- 

 sponds with that of the rectus in OrnithoryncMis ; and I am disposed 

 to think that, in this animal, the rectus, at least in its posterior 

 moiety, is represented by the homologue of this muscle, which has 

 extended laterally over the dorsal face of the enormously enlarged 

 homologues of the rami of the ypsiloid cartilage. 



However this may be, it must be recollected that it is only the 

 extreme ends of the rami which lie dorsad of the recti, and that, in the 

 rest of its extent, the epipubis of Salamandra is firmly fixed to the fascia 

 of the external oblique, which forms the front wall of the sheath of the 

 rectus. The homology of the epipubis with the marsupial bones is 

 determined by the essential identity of the relations of the two to the 

 tendons of the external oblique muscles. 



It seems to me that, in such a pelvis as that of Salamandra, we 

 have an adequate representation of the type from which all the dif- 

 ferent modifications which we find in the higher Vertebrata may have 

 taken their origin. 



In the lizards and the Chelonia the iliac and obturator axes ha^e 

 inclined forwards, and the epipubes have been reduced to such rudi- 

 ments, as have been described in chameleons and in some tortoises. * 



In the crocodiles, with the same general pelvic characters, the 

 cotyloid end of the pubis retains its imperfectly ossified condition, 

 while the epibubes represent the vastly enlarged rami of the sala- 

 mandrine epipubis. 



In the Omitlioscelida and in birds, the ilia elongate, but it is the 

 modification of the pubes and ischia which is the most characteristic 

 feature of the pelvis, and the epipubis vanishes. 



In the Pterosauria and in the Dicynodonts, the salamandrine non- 

 development of an obturator fontanelle persists ; and, in the former, 

 the sessile rami of the epipubis appear to be represented by the so-called 

 marsupial bones. 



* Hoffmann, " Beitrage zur Kenntniss des Beckens der Amphibien und Kepti- 

 lien," " Nied. Archiv fur Zoologie," Bd. 3, p. 143, 1876. 



