96 SHOULDER-GIRDLE AND BREAST-BONE. 



This minute, nearly vertical Limb-girdle is, by its histological development, subdivided into 

 three superimposed morphological regions. 



The first of these is the supra-scapula (s. so.), which is sub-lunate, and broader than deep : 

 it is only ossified, as in Lizards generally, by endostosis. Continuous with this is the scapula 

 (sc.), a phalangoid ray, having its broad upper and lower margins sloping downwards in front ; 

 a long, narrow, sub-cylindrical body, and a foot-shaped base, which is scooped on its outside, 

 posteriorly, to form the upper half of the neat glenoid cavity (fig. 9.gl.). The whole of the 

 scapula is invested with an ectosteal sheath, so that it is a perfect shaft-bone, with the supra- 

 scapula arrested as its epiphysis. The lowest division is twice as large as the uppermost, and is 

 like it in shape, only that it is inverted, the blunt-pointed end being directed forwards and 

 upwards, that of the supra-scapula being backwards and downwards. This is the coracoid (cr.), 

 or rather the whole coracoidean region, pra3-, epi-, and post-coracoid all in one low, broad, 

 thoroughly ossified shaft-bone. Outside, near the hinder margin, it makes the bottom part of the 

 glenoid cup (fig. 8, gl.) ; and a little below its articulation with the scapula, in front, the nerve- 

 passage can be seen (fig. 10). This coracoid is very thick at its sinuous upper margin, scooped 

 at the middle, and somewhat thickened again in the extended epicoracoid region ; this part is 

 nearly invested with the general ectosteal covering, for but a little of the inner bone can be seen. 



This is a very generalised structure, but in respect of its perfectly ossified scapula it stands 

 higher than my next example of a Lacertilian Shoulder-plate ; but there is no " coracoid cleft," 

 such as we have seen in the Amphibia, and shall see also in most of the Lacertilia. 



Professor HyrtPs preparation shows no splint-bones, as far as I can see with a pocket 

 glass : and in this, as well as in the undivided coracoid, we have the Chamaeleon forestalled 

 (see PI. 1 1, figs. 4, 5). 



In the whole range of vertebrate morphology there is nothing more beautiful or more 

 instructive than the relatively large Sternum of Ckirotes ; for if the Sternum of the Human 

 embryo were to be demonstrated apart from the costal girdles, one diagram would serve to explain 

 both that and what we find in this little Snake-lizard. The three typical transverse divisions, 

 namely, the prae-, meso-, and xiphi-sternum, are all perfectly marked out here, whilst the greater 

 part of the primordial line (the thoracic " fontanelle," so to speak) is persistent. If the ribs had 

 not been arrested there might have been seen the counterpart of our first dorsal (and perhaps 

 also, as in many Lizards, of the kst cervical) ribs, attached to the sides of the manubrium, 

 behind the " coracoid grooves ;" at the junction of the prse- and meso-sternum there might 

 have been the exact homologue of our second ribs ; then a series of thoracic ribs ; and lastly, 

 free xiphisternal horns, as in most Mammalian embryos, and also in some adults, as in certain species 

 of Pangolins (e.g. Manis longicauda and Pholidotus africanus, see PI. 22, fig. 13). This is a most 

 striking instance of what we so frequently meet with, but which is always puzzling at first sight, 

 namely, the cropping out of the distal part of an arch (or arches), the sides of which are aborted. 

 The correlation of the prae-sternum with the broad coracoids has resulted in its being five times 

 the breadth of the meso-sternum ; it is one and a half line in length and one and one fifth line in 

 breadth, and is sub-hexagonal in outline. The antero-lateral margins (Plate VIII, fig. 8, p. st.) 

 are concave (lunate), and they end in a subfalcate horn on each side; these horns are sepa- 

 rated by a cleft, which is wide at first, then narrow, and broad again where it terminates near the 

 middle of the prae-sternum. The hinder half of the middle is occupied by an isthmus of soft 

 cartilage, then an oval fenestra (p.st. f.), and then there is a smaller isthmus, which is ossified as 



