196 SHOULDER-GIRDLE AND BREAST-BONE. 



double. The xiphi-sternum is free, and single, except in Manis (some species), but often 

 shows signs of its symmetrical origin ; there may be more than one (serial) " metosteon," 

 but there is no differentiation of the " ento-sternum" (save in a trifling degree, in some Bats), 

 and, therefore, there is no " lophosteon" except when the manubrial keel has an epiphysis, as 

 in some Armadillos ; and no " urosteon." The vertebral ribs are variously connected with the 

 sternal, by continuous cartilage ; by intercalation of fibrous tracts ; or by synovia! joints ; 

 and there is not unfrequently an " intermediate rib." The sternal ribs, however solid in the 

 adult, are always ossified endosteally at first. 



Ordo " MARSUPIALIA." 



Examples. Didelphys, Dasyurm, Phalangista, Halmaturus, Bettongia, Pdrogale, P/iascol- 

 arctos, Phascolomys} 



The scapula is, essentially, very uniform in all the Marsupials (see Plates XIX, XX, exclud- 

 ing fig. 17 in Plate XIX) ; the supra-scapular region (s. sc.) is very narrow, and little liable to 

 ossification, but the body of the scapula is large and outspread ; it is divisible into three regions 

 (which are true morphological territories), namely, the scapula proper or post-scapula, the roeso- 

 scapula, and the prse-scapula. If a line be drawn in front of the crest, from the narrowest part 

 of the neck of the scapula to the upper outspread end of the crest, it will give the pra-scapular 

 region: the crest itself, with the " acromion process," and the tract of bone out of- which the 

 crest rises, is the "meso-scapula ;" all behind that is the scapula proper or "post-scapula." 

 The prae-scapula is well shown in the Marsupials (see Plate XIX, figs. 1, 8, and 13, and Plate 

 XX, figs. 3, 5, 8, and 11, p. sc.); in all it projects forwards, forming an obtuse angle; and below, 

 is separated from the coracoid rudiment by the " supra-scapular notch," 2 a true morphological 

 notch; whilst above, it melts insensibly into the "meso-scapula." The pra>scapula has the 

 greatest vertical extent in Didelphys (Plate XIX, fig. 1), forms the acutest angle in the Wombat 

 (Plate XIX, fig. 13), and is least developed in Bettongia (Plate XX, fig. 8). The "meso- 

 scapula " forms a large crest in all ; this is most outspread in Didelphys, where it, exceptionally, 

 sends forwards a bilobate acromion ; in the others, the acromion (ac.) is falcate : in all, the 

 extremity continues soft, even to adult age. In none is there any cleft separating the meso- 

 scapula from the scapula or pra3-scapula ; but the notch separating the acromion from the 

 base of the scapula is rounded and deep (see in the Wombat, Plate XIX, fig. 16). There is no 

 free crest on ^the post-scapula, dividing the " infra-spinous fossa " into two valleys ; but the 

 hinder edge of the base is thick. The coraooid (cr.) is small in all ; it has a somewhat hooked 

 form, and is thick at the base; its ossification is by a separate endosteal patch (see DidelpJiys, 

 Plate XIX, fig. 1, and Phalangista, fig. 8, cr.). The clavicle (cl.) is present in all these examples; 



1 The Didelphys, the Dasyure, and the Koala were adult; the Phalariger was a young male, 

 measuring eight inches from snout to root of tail (the two points from which I measure all land 

 Mammals) ; the larger specimen of Halmaturus Bennettii measured 10 in. 4 1.; the smaller, 3 iu. 2 I. ; 

 Petrogale ocanthopus, 3 in. 1 1.; Bettongia Grayi, 2 in. 6 1.; and the Wombat, 11 in. 



! This is the anthropotomical term; " coraco-scapular notch" would lie more correct. 



