1905.] THERIODONT REPTILE DIADEMODON. 101 



Diaclemodon in having no notch between the head and the tro- 

 chanter major, but differs in having the trochanter minor very 

 feebly developed. On the whole the mammalian femur which 

 most resembles that of Diademodon is the femu.r of Echidna. In 

 Echidna, however, the trochanter major is less strongly developed, 

 the head has a distinct neck, and the trochanter minor is directed 

 more inwards than backwards. But these points are not of much 

 importance, as they are found to vary greatly according to the 

 habits, in even closely allied mammals ; and there is little doubt 

 that the femur in Echidna is fundamentally similar to that in 

 Diademodon. In Phascolomys the small trochanter gives the 

 proximal end a superficial resemblance to that of Diademodon., 

 but the two bones are not very closely related. A more important 

 affinity is seen in the femur of Dasypus. Here the small tro- 

 chanter resembles considerably that of the Theriodont, and the 

 trochanter major is similarly directed forwards. The presence of 

 the third trochanter, however, and the deep depression in the 

 head for the teres ligament show that the two bones are possibly 

 not any more nearly related than are those of the Marsupial and 

 Theriodont. At the lower end of the bone the condyles are more 

 developed than in Echidna and less than in Phascolomys. The 

 cartilaginous surface can be traced from the one condyle to the 

 other over the intercondylar hollow. From the shape of the 

 portions of the condyles preserved, I think one is justified in 

 concluding that Diademodon stood, when at rest, with the femur 

 directed downwards and forwards, making an angle of 45° with 

 the surface of the ground. In this respect it agi'ees with Ano- 

 modonts and Mammals generally. 



The following are some of the principal measurements of the 



femur : — 



millim. 



Greatest length about 91 



"Width of proximal end ,, 37 



Width of middle of shaft „ 8*5 



The small vertebra which is preserved is believed to be one of 

 the last of the dorso-lumbar series. In structure it is exceedingly 

 mammal-like. The centrum seems to be about as broad as long, 

 but is apparently much broader in front than behind, owing to the 

 autogenous tivansverse process or rib being attached to the side of 

 the anterior point of the centrum. This transverse process has a 

 very large attachment, the lower part of which is anchylosed to 

 the centrum and the upper part to the arch. There is apparently 

 a small foramen passing from fi'ont to back neai- the line of the 

 suture of the arch and the centrum, and in reality making the 

 transverse process or rib double-headed. A part of the inner end 

 of the transverse process comes a little further forward than the 

 anterior end of the centrum and appears to form a slight articu- 

 lation with the centrum in front. Passing outwards the transverse 

 process becomes slender and is directed forward. Whether it after- 



