188 ME. H. G. SBELEY ON OSSEOUS KESEMBLANCES 



formed of elements placed one behind the other, as iu mam- 

 mals. 



The limb-bones with their epiphyses remind us of mammals' 

 and Salamanders', though in the larger bones the resemblance of 

 form is small. Bears, like Lizards, have the ulna larger than the 

 radius : mammals have the bone compressed from side to side as 

 it is in Lizards ; but in mammals the proximal end is usually 

 prolonged beyond the articulation. The carpus, metacarpus, and 

 phalanges are very like in form to those of mammals, except that 

 in Lizards the phalangeal bones are more elongated. 



There is considerable resemblance in the pelvis to that of a 

 mammal, so that if the pelvis w^ere turned round about the 

 sacrum so that the ilia were directed forward, little would be 

 needed to make the pelvis mammalian, beyond the prolongation 

 mesially backward of the pubes to meet the ischia and so form 

 obturator -foramina, a suppression of the prepubic angle of the 

 pubis, and an expansion of the free end of the ilium. 



The femur is unlike that of any mammal in having the inner or 

 tibial trochanter of the proximal end greatly developed, and the 

 outer or great trochanter suppressed — as well as in having the 

 articular head compressed, which is also a feature of the humerus. 

 The inner trochanter of the femur of Ornithorhynclius is similar ; 

 but the bone in no other respect is like that of Lizards. 



There is no patella in Lizards. The tibia diifers from most 

 mammals' in being, at the proximal end, compressed from front to 

 back ; in Dasyurus it is subeylindrical. The fibula differs from 

 mammals' in articulating with the side of the femur. The tarsus 

 is not mammalian ; and the other bones of the foot diifer from 

 mammals' chiefly in their great length. 



§ 2. The Avian Characters of Lizards. 



The single premaxillary extends between the nares and between 

 the termination of the nasal bones, after the manner of birds ; 

 but in birds the lateral rays of the bone diverge backward, and 

 form that part of the palatal border which in Lizards is made by 

 the maxillary bones ; and in Struthious birds the premaxillaries 

 make a conspicuous part of the palate. 



The free motion of the quadrate bone is avian ; but the bone 

 does not articulate with the wall of the brain-case as in birds. 

 The basisphenoid in Struthious birds gives off" similar lateral pro- 



