398 



Prof. Huxley on the 



[Mar. 6, 



(Plate 8, fig. 2), or that of a Chelonian, it will be observed that the 

 resemblance between the former and the Sauropsidan pelvis is, in most 

 respects, closer than that which it bears to the higher Mammalian pelvis. 

 In the reptiles both the pnbes and the ischia unite in a ventral 

 symphysis ; the pubis has a strong pectineal process, which acquires 

 very large dimensions in the Ghelonia ; the metischial processes are 

 also often very strong. Nevertheless, there is an important difference, 

 for, in all these animals, the iliac axis is either nearly perpendicular 

 to the sacral axis, or slopes from above downwards and forwards ; 

 the obturator axis also inclines downwards and forwards. Hence, in 

 most Lacertilia and Chelonia, the pubes slope forwards very obliquely, 

 while the ischia come more and more forwards. In other words, such 

 modifications of the pelvis as occur in the Lacertilia and the Chelonia 

 are of an opposite kind to those which take place in Mammalia. 



The same thing is true of the Crocodilia (Plate 8, fig. 3). Here the 

 ilium is much broader than in the lizards and the Chelonia. This broad- 

 ening is effected by the expansion of the ilium, both in front of and behind 

 the iliac axis, which retains about the same inclination to the sacral axis 

 that it has in lizards. The ischia have but small metischial processes, and 

 their long axes lie further forwards than in most lizards. The obturator 

 axis inclines forwards, and the iliopectineal axis is parallel with the 

 sacral axis, as in lizards. As in Echidna, a space of the inner wall of the 

 acetabulum is fibrous. The lower boundary of this space is constituted 

 by a prolongation of the anterior end of the cotyloid extremity of the 

 ischium. The interval between this and the anterior end of the ilium 

 answers to the cotyloid end of the pubis in a lizard, but it does not 

 ossify. The pubis corresponds exactly in direction with that of a lizard, 

 but its form is very different. At first narrow and rounded, it gradually 

 flattens from above downwards and, at the same time, widens into a 

 broad trowel-shaped plate of cartilage enclosed in a dense fibrous peri- 

 chondrium, which lies close beside the middle line in the ventral wall of 

 the abdomen (Plate 8, fig. 12). Each of these flat cartilages is distinct 

 from its fellow throughout the greater part of its extent; but, posteriorly, 

 the two approach, and are united by a broad and strong ligamentous 

 band (Sij. p. /.). The bony portion of the pubis commences just outside 

 the acetabulum and extends to this band, terminating by a curved edge 

 directed inwards and forwards. It is the osseous portions of the pubes 

 which are commonly described as the entire pubes of the Crocodilia, 

 and much speculative ingenuity has been expended upon the interpre- 

 tation* of these apparently anomalous elements of the pelvis, which 



* For the latest of these interpretations see Hoffman's excellent memoir, 

 "Beitragezur Kenntniss des Beckens der Amphibien und Reptilien." " Nied. 

 Archiv fur Zoologie," 1876. I cannot but think that had Professor Hoffman studied 

 the crocodile's pelvis in fresh or spirit specimens, he would not have put forward 

 the hypothesis that the pubes of the crocodiles are " epipubes." Rathke's account of 



