222 SHOULDER-GIRDLE AND BREAST-BONE. 



sternum, however, it approaches the Pig (fig. 20, m. st.), for the last (seventh) segment has sym- 

 metrical pleurostea ; there is, however, no xiphoid process : in this the Tapir is unique. In an 

 Embryo-Pig, four inches long (fig. 10, two and two-thirds diameters) the Sternum has the same 

 form as in the Ruminant (Bos, fig. 2 ; Tragulus,^. G), but the prse-sternal beak is more produced 

 than even in the little Musk-deer, and it is carin ate below (fig. 11, p. st.). The facets for the first 

 ribs (which are unsegmented) are large and elevated, the rest of the perfect ribs jut into lateral 

 fossa?, and are segmented where they form an acute angle. The whole of the Sternum and the 

 sternal ribs are still unossified, so that ossification is later than in the Ox ; but the shafts of the 

 vertebral ribs (v. r.) are creeping downwards. A perfect joint, apparently synovial in the adult 

 (fig. 12), is formed between the prae- and meso-sternum ; the pra> and the first meso-stcrnal joint are 

 ossified unsymmetrically by endostosis ; then there are three pairs of meso-sternals (fig. 12, m. st., 

 adult, one fourth nat. size), and a xiphoid bone (x.), which becomes suddenly narrow in its hinder 

 half. In old Peccaries additional ossicles appear in the Sternum. In a Hyrax, a week or two old, 

 the sternal bones are already well ossified, appearing, as I suppose, as endosteal patches very early, 

 as in the Ox-embryo ; there is a true joint (evidently synovial) between the prae- and meso-sternum 

 (fig. 9, p. st., m. st., nat. size) : the sternal segments are narrow, as in the Rodents. At this early 

 age the sternal ribs (s. r.) are not ossified, and the vertebral ribs have a large piece soft below. 

 In a Hyrax, one third adult, this remaining part has in it an endosteal patch, or " costa inter- 

 media" (fig. 8, i. r. 2) ; this is also to be seen in the adult (fig. 7, i. r. 2, both reduced in size 1 ). 

 The reappearance of the "intermediate rib" in the Hyrax is noteworthy ; this Lacertian segment 

 has been seen to crop-out in the Monotremes, the Armadillos, the Chryscochlore (amongst the 

 Insectivora), and in the Cetacea, where it comes nearest to its counterpart in the Chamseleon (Plate 

 XI, fig. G, i. r.). The synovial joint between the vertebral and sternal ribs, which appears first in 

 the Crocodile, is universal in the Bird-class, and breaks out again in certain Edentata, for instance, 

 Dasypus, Cyclotliurus, is constant in the Herbivora : in the Cetacea, Sirenia, and the Edentate 

 Pangolins, the segmentation is not so perfect. 



Ordo " PRIMATES." 

 Examples. Mycetes, Jaccfais, Cercocebus, Pilhecus, Homo. 



This group might have followed either the Sciurine Rodents or the Bats ; they both approach 

 it, but do not altogether agree with it. It is easily characterised : the scapula is obliquely 

 triangular (Plate XXX, figs. 9, 12, 17, 21), and the processes are well developed; the clavicle 

 and its correlates are all present, the " omosternum " being converted during growth into a 

 "meniscus." The manubrium is moderately broad, and generally separated by a transverse tract 

 of fibre from the continuous meso-sternum ; and the xiphi-sternum is only partly severed from the 

 meso-sternum by notches, and is only moderately broad terminally. The Sternum is broad in 

 flat-chested Man, and three of the meso-sternal region are ossified by symmetrical " pleurostea " 

 (fig. 15) ; the whole of the meso-sternum is thus ossified in the Orang (fig. 16), and it has no 



The first costal arch of the Peccary is not segmented at the infero-lateral angle like the 

 remaining ribs, whether fixed or " floating ;" and the sternal ribs are ossified by endostosis (fig. 8, s. r.) : 

 supernumerary ossicles appear in the sternum of the adult, as in Tragulus javanicus. In the young 

 Indian Elephant, as in the Tapir, the last meso-sternal is symmetrical. 



