1887.] 



On the Os Pubis in Crocodilia. 



237 



occupies the place of the pubis, and so it is manifest that if the pubis 

 enters into the acetabulum in crocodiles, it must be found in the 

 anterior process of what is commonly named the ischium, which fills 

 the anterior corner of the pelvic basin. And since no exception to 

 this position of the pubis among vertebrates is known, by which it 

 articulates with the ilium, the conclusion is legitimate, in the absence 

 of evidence to the contrary, that a bone which does not unite with the 

 ilium by bony union, and which is carried in front of a process which 

 occupies the usual position of the pubis, cannot be the pubic bone. It 

 would be equally unprecedented for the pubis and ischium to be 

 connate in a reptile, were it ilot that this condition is already esta- 

 blished in the existing Amphibia, and were there not strong reasons 

 for regarding the crocodiles as descended from extinct allies of the 

 Amphibian class ; while in an early stage of development all the pelvic 

 elements in crocodiles are connate. Hence I concur with Professor 

 Huxley in regarding Professor Hoffmann's identification of the pelvic 

 acetabular cartilage as the pubis as untenable. 



Professor Hoffmann regards the bone which is commonly identified 

 as the pubis as being the pre-pubis.* Professor Huxley, on the other, 

 hand, regards it as being a portion of the pubis, and bases his iden- 

 tification mainly on the relations of this bony element to the pelvic 

 muscles. There is an a priori objection to the latter interpretation, 

 because it would introduce a joint in the middle of the pubis, making 

 one part connate with the ischium, and the other part a free bone. Of 

 such a condition I am not aware that vertebrate osteology offers any 

 example, and the improbability against it being a true interpretation 

 seems to be great. That a bone may ossify from several centres 

 is evident from the bones of Mammalia and certain young birds and 

 lizards; but in crocodiles none of the bones are thus characterised, 

 and therefore I can only conclude with Hoffmann, that the ossifica- 

 tion is a distinct element of the skeleton, which is connected with the 

 pubic portion of what I term the ischio-pubic bone, and is in the 

 position of the pre-pubic bone ; but it does not necessarily follow that 

 it is identical with the pre-pubic cartilage, which has been termed by 

 Hoffmann and Huxley the epipubis. For the cartilage, whether in 

 Amphibians or Mammals, is developed from the median line of the 

 pubic symphysis ; while in crocodiles the pubes do not form a 

 symphysis, because they are not developed distal ly, and the pre-pubic 

 ossification is situate immediately below the acetabulum, in the posi- 

 tion of the pectineal process ; so that while the Amphibian cartilage is 

 in the position of the marsupial bones of mammals, the crocodilian 



* Professor Haughton (' Ann. Mag. Nat. Hist.,' vol. 1, 186S, p. 2S2) bases the 

 nomenclature of the bones on the muscular anatomy, and terms the reputed pubis 

 the marsupial bone ; the ischium then becomes the pubis; while the ilium is the 

 ilium in its anterior part, and the ischium in the posterior part. 



T 2 



