BETWEEN TYPICAL EEPTILKS AND OTHER ANIMALS. 159 



is almost, if not entirely, excluded, though not in the same way 

 as in the Crocodile. In many mammals the articulation is chiefly 

 formed by ilium and ischium, as in JEchidna and the Orang. In 

 the Crocodile the ilium and ischium almost meet again in front 

 of the articulation so as to form an acetabular foramen. As a 

 whole the Crocodilian pelvis most closely resembles that of the 

 Seals, though it meets the sacrum more nearly at a right angle. 

 The ilium of the Seal differs from that of the Crocodile in being 

 anchylosed to the ischium and pubis, in the oblique way (mam- 

 malian way) in which it meets the sacrum, and in not being 

 prolonged so far either backward or forward. As among the 

 mammals, the pubis is the slender bone, while the ischium is 

 larger. But in mammals the ischium usually has an osseous 

 union with the pubis along the median abdominal line, which 

 condition does not obtain in Crocodiles. Speaking generally, 

 there is considerable resemblance in form respectively between 

 the pubis and ischium of mammals, such as the Orang, and the 

 Crocodile, though the bones in the Crocodile are intermediate in 

 length between those of the Orang and the Seal. 



The hind-limb bones of Crocodiles, like the bones of the fore 

 limb, are distinguished from those of many mammals by wanting 

 epiphyses. The femur, like the humerus, is distinguished by the 

 proximal end wanting the external trochanter so characteristic 

 of mammals, which latter usually have the proximal articular 

 surface more convex. The external trochanter which marks the 

 middle of the shaft in many mammals, such as Pachyderms like 

 the Rhinoceros, is also moderately developed in the Crocodile ; but 

 there is no representative of the inner trochanter feebly deve- 

 loped in some mammals, such as Kangaroos, Tapir, Beaver, 

 EnTiydra, which is characteristic of the Dinosauria. The distal 

 end is much more like the femur of mammals than is the proxi- 

 mal end, and may be compared to that of the Brown Bear, 

 though in most mammals an antero-posterior thickening of the 

 distal end constitutes a character which is not repeated in Croco- 

 diles. 



The Crocodile has no patella. The tibia is more cylindrical in 

 its shaft than is the case with most mammals ; and the cnemial 

 crest, which many mammals have in common with birds, is not 

 developed. Among placental mammals the Porcupine has a tibia 

 of similar form and proportion ; but its articular surfaces are 

 better defined and somewhat different. A nearer resemblance is 



