MONOTREMATA. 



379 



transversely, convex vertically, in the Echidna ; 

 it is hardly definable when the cartilage is 

 separated from the bone ; but the patella itself 

 is well developed, and ossified in both Mono- 

 tremes (Jig. 173, A, p). 



The tibia is straight in the Echidna, but 

 bent, with the convexity next the fibula, in 

 the Ornithorhynchus; its cristre are slightly 

 marked. 



Thejibula is slightly bent in the Echidna, 

 but is straight in the Ornithorhynchus ; in both 

 Monotremes it is longer than the tibia by the 

 extent of a process which rises upwards beyond 

 the proximal articulation of the fibula, and 

 most strongly expresses the analogy of this 

 bone with the ulna: this process (Jig.\73, A, t>) 

 reaches half way up the back of the femur in 

 the Ornithorhynchus, and, like the olecranon, is 

 greatly expanded at its termination. Cuvier* 

 indicates the resemblance of this structure in 

 the Monotremes with the fibula and the super- 

 numerary bone imposed upon its enlarged prox- 

 imal end in the pedimanous Marsupials. 



The tarsus (Jigs. 178, 179) consists of a 

 scaphoid ()> astragalus (6), a calcaneum (c), 

 three cuneiform bones (d,e,/), and a cuboid (g) 

 in the Echidna ; but the cuboid in the Onntho- 



Fig. 178. 



Bones of hind- foot, Echidna hystrix, (Cuvier.) 



rhynchus is divided into two bones, as in some 

 Reptiles, one for the fourth and the other for 

 the fifth metatarsal bones. In both Mono- 

 tremes there is a sesamoid bone (Jig. 178,*) 

 placed at the interspace between the astragalus 

 and the naviculare; a second supernumerary 

 bone (* *) is articulated to the posterior part of 

 the astragalus, and supports the perforated spur 

 which characterizes the male sex (Jig. 173, 



K,rf). 



The calcaneum of the Ornithorhynchus ter- 

 minates by sending outwards a short obtuse 

 tuberosity ; in the Echidna this part is more 

 slender, and is singularly directed inwards 



and forwards, nearly in a line with the digits 

 (fig. 179, e). 



The astragal us in the *ig- 179. 



Ornithorhynchus pre- 

 sents a double troclilea 

 above for the tibia and 

 fibula, and a depres- 

 sion on its inner side, 

 which receives the in- 

 curved malleolus of the 

 tibia, almost as in the 

 Sloths. The toes have 

 the same number of 

 bones as in other Mam- 

 mal ia; their size and 

 form are more alike in 

 the two Monotrema- 

 tous genera than those 

 of the fingers: the un- 

 gual phalanges, like 

 the claws they support, 

 are more curved than 

 those on the fore foot, 

 but like them they are 

 perforated on their in- Bones of hind-foot, plantar 

 ner and concave side aspect, Echidna setosa. 

 (Jlg.\79). (Original.) 



OF THE MUSCULAR SYSTEM. 



The figure (180) here given from Meckel* il- 

 lustrates some of the most instructive peculiari- 

 ties of the muscular system of the Ornithorhyn- 

 chus. The animal is dissected from the ventral 

 surface; the great cutaneous muscle, the ' pan- 

 niculus carnosus' (1), is reflected from the right 

 side, and the deeper-seated muscles are shown 

 on the left. The panniculus carnosus, which is 

 remarkable for its thickness, encompasses nearly 

 the whole body, adhering most firmly to the 

 external skin, but separated from the subjacent 

 muscles, especially where it covets the thorax, 

 abdomen, the arm, and the thigh, by a copious 

 and lax cellular tissue; and in the female, at 

 the abdominal region, by the mammary glands. 

 The fibres are chiefly longitudinal, but at the 

 lower part of the neck become transverse. The 

 obtuse posterior end of the muscle is attached 

 by three or four fasciculi to the dorsal aspect 

 of the transverse processes of the caudal 

 vertebrae. The legs and the arms protrude 

 through oblique apertures in this muscular 

 tunic ; some of the anterior fasciculi are in- 

 serted by a short tendon into the pectoral ridge 

 of the humerus; and others, still more anterior, 

 are attached to the cranium, the lower jaw, and 

 lower lip. A strip of fibres, which is cut off 

 at 1*, is attached to the os hyoides; another 

 fasciculus (!') spreads over the cheek-pouch, 

 and assists in emptying that receptacle of the 

 food. 



The trapezius (9) is divided into two muscles ; 

 the posterior portion is an oblong slender tri- 

 angle arising by a broad tendon from the tenth 

 and eleventh vertebrae and ribs, and inserted by 

 a short strong tendon in the anterior extremity 

 of the spine of the scapula; the anterior portion 

 is shorter, but broader, and is subquadrangular; 

 it arises from the occiput and tendinous raphe 



* Osscm. Foss. v. pt. i. p. 153. 



De Ornithorhyncho, &c. tab. v. 



