21G SHOULDER-GIRDLE AND BREAST-BONE. 



scapula of the Cat has a deep spine, which leans backwards over the infra-spinous fossa (fig. 1, m. 

 sc.) ; this spine becomes free below, and gives off a broad " metacroraion " (m. ac.) ; the acromion 

 turns forwards. The area of the " supra-" and " infra-spinous fossas" is nearly equal ; in the 

 adult the supra-scapular region is small, and ossifies very slowly ; the coracoid (cr.) is very small, 

 and sends inwards and backwards a small curved beak. In the newly-born Leopard the scapular 

 bones are much advanced (fig. 3, p. sc., sc. one and one-third diameters), and are united 

 by a dentate suture, which lies further off from the spine than in the embryo Cat ; this is a 

 growth-change : the supra-scapular (coraco-scapular) notch is a large half-moon. In the newly- 

 born Polar Bear (fig. 4, natural size), this notch is very small, deep, and rounded; the coracoid 

 boundary, below (cr.), is a very blunt projection from the glenoid cup ; and the prae-scapular bone 

 (p. sc.) only occupies a smallish square plot at the lower angle of the very broad supra-spinous 

 fossa. The spine of the meso-scapula (m. sc.) is deep, and leans backwards, as in the Cat, but 

 the acromion is not forked, and has a pyriform outline : the whole blade-bone at this stage is 

 nearly as broad as high, and the whole supra-scapular region (s. sc.) is semioval in outline. The 

 embryonic form of the Bear's scapula is much like that of the adult Seal (Phoca grcenlandica, 

 fig. 8, one-quarter natural size), but does not curve backwards so much, and has a larger acromion ; 

 yet the scapulae are of precisely the same type ; the leaning back of the spine at the middle, the 

 bulging of the pra-scapula, the size of the supra-scapular notch, and the great abortion of the 

 prae-coracoid these are alike in both. The Seal has a very large supra-scapular epiphysis (s. sc.), 

 for in that type the scapula has something of the arcuate form seen in the Platypus. In the half- 

 ripe embryo of the Cat the clavicle and its correlates had not appeared ; nor could I find them in 

 the Polar Bear, just born ; but in the new-born Leopard (fig. 3, cl., p. cr., m. sc. s.) these parts are 

 present, although veiy small : they become one, twisted, styloid bony piece in the adult : there 

 is no omosternum. In the early stage of the Kitten (fig. 1) the Sternum shows a considerable 

 amount of commenced segmentation ; this, however, is only completed between the pra> and meso- 

 sternum (see fig. 3, p. st., m. st.). As yet, the first rib is not ossified in the vertebral region ; 

 nor is it segmented from the Sternum below ; the latter is not at all ossified. It terminates in 

 front in a short (p. st.), and behind in a rounded, oblong flap (x.); this latter becomes somewhat 

 outspread afterwards (fig. 3, x.), as shown in the new-born Leopard. In this instance we see the 

 first sternal rib segmented from the Sternum (s. r. 1) ; the prse-meso-sternal transverse cleft, with 

 no successors ; the absence of cleft between the vertebral (v. r.) and sternal ribs ; and the phalangi- 

 form, ectosteal sternal bones (p. st., in. st., x.). The same things are seen in the young Bear 

 (figs. 5 and 6), but there is no transverse cleft behind the manubrium (p. st.) ; the last meso- 

 sternal (fig. 6, m. st.) has but just commenced, and there is, as yet, no " metosteon " in the 

 short xiphoid (x.). In the adult Otaria (fig. 7, one-quarter natural size) there is, as far as I 

 can see in the newly dried Sternum, no perfect transverse segmentation of the Sternum, which 

 ossifies by cctostosis ; nor is there any segmentation of the vertebral from the sternal rib (v. r. 1, 

 s. r. 1) -. these latter do not ossify, except, perhaps, slightly, in extreme old age. The cervical part 

 of prse-sternum (p. st.) is very long ; is carinate below, and continues soft in front ; the long, 

 elegant, spatulate xiphoid (x.) has a long " metosteon," which does not occupy all the " handle " 

 of the spatula, the rest, and the pyriform end, continuing soft. 



