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The marsupial bones are elongated, flattened, often more or less curved ; they are 

 expanded at the proximal extremity, which sometimes, as in the Wombat, is articulated 

 to the pubis by two points : they are relatively longest, straightest, and most slender 

 in the Bandicoots, flattest, broadest, and most curved in the Koala, and shortest in 

 Myrmecobius, where they do not exceed half an inch in length. In Thylacinm they 

 are not ossified. The cremaster muscle in the male, and its homotype in female, winds 

 round the sclerous or osseous ' internal pillar ' of the abdominal ring in its passage 

 to the testicle or to the mammary gland. 



The femur is a nearly straight cylindrical bone, having a hemispherical head, sup- 

 ported on a very short neck, especially in the Petaurists, and situated here almost in 

 the axis of the shaft, above and between the two trochanters, which are nearly of equal 

 size. In the Kangaroos and Potoroos the head of the thigh-bone is turned more 

 inward, and the outer or great trochanter rises high above it ; in other Marsupials the 

 great trochanter is less developed. In all the species a strong ridge is continued a short 

 way downward from the outer side of the trochanter ; and this ridge is so produced in 

 the Wombat as almost to merit the name of a third trochanter. At the distal extremity 

 of the femur the external condyle is usually the largest, the internal rather the longest. 

 The intermediate groove for the patella is well marked in the Bandicoots, where that sesa- 

 moid is ossified, but is broad and very shallow in the Phalangers and Dasyures, where 

 the tendon of the rectus muscle is thickened and has but a few specks of ossification ; 

 the rotular surface in the Petaurists, Wombats, and Koala, is almost plane from side to 

 side. In Ifacrojyodidce the back part of the outer condyle is grooved, but not so deeply 

 as in birds. 



The tibia presents the usual disposition of the articular surface for the condyles of 

 the femur ; but in some genera the outer surface is continuous with that for the head 

 of the fibula. In the Kangaroos and Potoroos the anterior part of the head is much 

 produced. A strong ' procnemial' ridge is continued down from this protuberance for 

 about one sixth the length of the tibia. In the Koala and Wombat, as in the Opossums, 

 Dasyures, Phalangers, and Petaurists, the shaft of the tibia is somewhat compressed 

 and twisted; but in the Kangaroos, Potoroos, and Bandicoots the tibia is prismatic 

 above, and sub cylindrical below. The internal malleolus is very slightly produced in 

 any Marsupial, but most so in the Wombat. 



The fibula is complete, and forms the external malleolus in all the Marsupials. In 

 Macrotis, it is firmly united to the lower part of the tibia, though the line of separa- 

 tion be manifest externally. In most Potoroos and Bandicoots it is in close contact 

 with the corresponding part of the tibia, but can be separated from that bone. In the 

 Kangaroos the fibula is also a distinct bone throughout ; but it is remarkably thinned 

 and concave at its lower half, so as to be adapted to the convexity of the tibia, with 

 which it is in close contact. In each of those genera, therefore, in which locomotion is 

 principally performed by the hinder extremities, we perceive that their osseous structure 

 is so modified as to ensure a due degree of fixity and strength; while in the other 



