182 ME. H. G. SEELET ON OSSEOUS RESEMBLANCES 



In the pelvis the shortness of the ilium in marine Chelonia is 

 a character which is approximately Crocodilian, but it is rather 

 like a less distant removal than a mark of affinity : the form of 

 the ischium, too, is least dissimilar in marine Cbelonians. 



The approximation of the tibia in Emysaura and Chelone to 

 the triangular form is Crocodilian. 



There is a general resemblance in the character of the articular 

 surfaces at the joints, and in the absence of epiphyses ; but in 

 the Chelonia the sharpness of definition increases considerably 

 with old age, probably more than in Crocodiles. 



§ 4. Lacertian Gliaracters of CheJonians. 



I do not recognize in the head any community of character 

 beyond such generalities as the vertical orbits in Iguana with 

 temporal fossee behind them. 



The pelvis is comparable both in the arrangement of the bones 

 and in their form. The ilium, however, is attached to the sacrum 

 by the middle of its inner surface, and not by its free end as in 

 Cbelonians. As in Emysaura, the Lacertian pubes and ischia do 

 not meet each other mesially so as to define obturator foramina. 

 The OS pubis of Lizards differs chiefiy in being perforated by the 

 obturator nerve, and in having the anterior digital process con- 

 nected by intervening bone with the anterior margin, so as to 

 make the form of the pubis roughly triangular, and not tri- 

 radiate as in Testudo. The ischium is like that in Emysaura ; so 

 that when the two bones meet mesially their ventral margins 

 form a Y-shape in Iguana, the cleft part being behind. 



The resemblance does not cease with the hind limbs, though 

 they are usually larger than the fore limbs in Lizards, while in 

 Cbelonians the inequality is much less marked, and only with 

 Emydians are the hind limbs visibly the longer. 



To make the femur of Emysaura comparable to that of Iguana, it 

 would only require that the bone should be straightened, and that 

 the trochanter on the fibular side (the great trochanter of mam- 

 mals) be entirely suppressed. 



There is a general resemblance of proportion and form between 

 the subtriangular tibia and fibula. The latter bone is usually 

 more slender. The comparison is best made between the Nilotic 

 Monitor and Emysaura serpentina. 



The proximal tarsals with the bones anchylosed into one row 



