144 



symphysis. How easy to suggest that tliis singlc symmetiical bone 

 may be the representative of the os penis lemoved irom the glans to 

 the root of the intromittent organ ! It is obviously a mere epiphysis 

 of the ischium. The circuraference of the acetabulum is alvvays in- 

 terrupted by a deep notch opposite the obturator-foramen, \vhich is 

 traversed by a ligamentous bridge, and gives passage to the vessels 

 of the Harderian gland lodged in the \vide and deep acetabular fossa. 



" The femur is a straight or nearly straight long cylindrical bone, 

 having a hemispherical head supported on a very thort neck, espe- 

 cially in the Petaurists, and situated here almost in the axis of the 

 shaft, above and betvveen the t\vo trochanters, which are nearly of 

 equal size. In the Kangaroos and Potoroos the head of the thigh 

 boneis turned more inwards, and the outer or greattrochanter rises 

 above it. In other Marsupiata the great trochanter is less developed. 

 In all a strong ridge is continued dovvnwards to a short distance 

 from the trochanter ; and this ridge is so produced at the lower part 

 in the Wombat as almost to merit the name of a third trochanter. 



" In the Wombat and Koala there is no depressiou for a ligamenium 

 teres \vhich ncvertheless exists in the latter. 



" The shaft of the bone presents no linečE aspera. The canal for 

 the nutrient artery commences at the upper third and posterior part 

 of the bone in the Koala, and extends do\vnwards, contrary \vise to that 

 in man and most other Mammalia. At the distal extremity of the 

 femur the external condyle is the largest, the internal rather the 

 longest. The intermediate antcrior groove for the patella is well 

 marked in the Perameles \vhere the patella is fuUy developed, but is 

 broad and veiy shallow in the Phalangers and Dasyures, \vhere the 

 tendon of the rectus is merely thickened, or offers only a fe\v irregular 

 specks of ossification ; and the corresponding surface in the Petau- 

 rists, Wombat and Koala, is almost plane from side to side. I find 

 distinct but small bony patellse in the Macropus Bennettii. 



"The tibia presents the usual disposition of the articular surface 

 for the coudyles of the femur; but in some genera, as the Wombat 

 and Koala, the outer articular surface is continuous -uitli that for 

 the head of the fibula. In the Kangaroos and Potoroos the 

 auterior part of the head of the tibia is much produced; and 

 in the young animal its ossification commences by a centre dis- 

 tinct from the ordinary proximal epiphysis of the bone. A strong 

 ridge is continued do\vn from this protuberance for about one 

 sixth the length of the tibia. In the Koala a strong tubcrosity 

 projects from the anterior part of the tibia at the junction of the 

 uijper \vith the middle thnd. In this species, and in the Wombat, 

 as also in the Opossums, Dasyures, Phalangers, and Petaurists, the 

 shaft of the tibia is somewhat comprcssed and twisted ; but in the 

 Kano-aroūs, Potoroos, and Perameles, the tibia is prismatic above 

 and subcylindrical below. The internal malleolus is very slightly 

 produced, perhaps most so in the Wombat. 



" The fibula is complcte, and fonus the extcrnal malleolus in all the 

 Marsupiata. In oue species of Hypsiprymnus, and in one species of 

 Perameles, it is firmly united to the lo\ver part of the tibia, thoiigh the 



