108 SHOULDER-GIRDLE AND BREAST-BONE. 



(u. c. f.), and the lower coracoid (I. c. f.). The scapular shaft-bone (sc., m. sc.) does not 

 reach the supra-scapular bone-substance above, nor the front margin of its own cartilage ; but 

 it joins the coracoidal shaft by a fine suture whicl^ runs obliquely across the fundus of the glenoid 

 cup. This well-ossified part of the scapula is an obliquely placed, stout, forked ray ; it leans 

 forwards, and the smaller front bar is almost horizontal : this lesser bar is the " acromion," or 

 " meso-scapula" (m. sc.), and the space between it and the main scapula is the " scapular 

 fenestra" (sc. f.) 1 



The anterior part of the supra-scapula, below, is not ossified ; it bulges, and then, suddenly 

 narrowing, becomes the prae-scapular belt (p. sc.). This belt widens in front of the meso- 

 scapula, and passes continuously into the prse-coracoid (p. cr.) ; it has undergone endostosis in the 

 hinder part of its lower half, and it forms the anterior boundary of the " coraco-scapular 

 fenestra" (c. s. f.) ; the lower margin of this fenestra is formed by a bar of the coracoid. This 

 latter bone (cr.) is surrounded in front and below by feebly ossified cartilage, the ossified part of 

 the cartilage forming a prae-epicoracoid hook of bone (p. cr., e. cr.) ; the marginal part of the car- 

 tilage, for a considerable extent, is persistently soft. The coracoid shaft-bone is not a little 

 remarkable ; it is three-rayed, stout, broad, and has each fork dilated at the end, and impinging 

 upon the feebly ossified rim. Its head articulates with the head of the scapula, and the hinder half 

 of this transverse suture lies in the glenoid cup. As the two rays of the scapula turn upwards 

 and forwards, so the three rays of the coracoid turn downwards and forwards ; and thus these five 

 rays spread, fan-like, forwards, separated by the large arrested clefts, and hedged in by the par- 

 tially ossified cartilage in front and below. If these horizontal clefts had been perfect, the 

 Shoulder-girdle plate of the Iguana would have formed five sub-parallel rays like the brachial 

 series of the Osseous Fish ; if vertical cleavage had taken place, obscurely indicated, histolo- 

 gically, by the arrest of the diaphysial bars, and by the subdivision of the feeble, internal bone, 

 then there would have been a double series, as in the limb of the Herring and the Polypterus ; 

 and this in the fixed root of the limb, and not in the free part. When I come to the Warm- 

 blooded Classes I shall show how large an amount of segmentation this marginal pras-coraco- 

 scapular band undergoes ; but we shall always find the stronger posterior part of the Shoulder- 

 plate very much indisposed to segmentation. I call the main bar of the coracoid simply the coracoid 

 (cr.) ; the upper bar is the root of the prse-coracoid, the rest of which is but little ossified ; and 

 then the second spur of the diaphysis runs down the meso-coracoid region (m. cr.) ; this shorter 

 bar and the main bone are bordered by the epicoracoid (e. cr.). In the head of the bone, in 

 front of the glenoid excavation, is seen the usual nerve-passage ; below, the left epicoracoid is 

 seen (Plate IX, fig. 2, e. cr.) to underlie the right. 



But these large many-windowed plates do not form the whole of the Iguana's Shoulder ; 

 they are strongly and elegantly undergirt with bones of an entirely opposite nature, which differ 

 from the endo-skeletal arch as the scaffolding differs from a building. In the Lizards generally, 

 with their expansible chests, there .are but three of these outer, subcutaneous bars ; but we shall find 

 a much greater number in the box-chested Reptiles (Chelonia), where we may say that the Ganoid 

 Fish reappears, not much happier with his higher powers, in the phlegmatic Tortoise. Plate IX, figs. 

 1 and 2, cl.,i. cl.) show these splint-bones in the Iguana; the symmetrical pieces are the clavicles, 



This fissure takes place at the opposite end of the scapula to what we find in the Batrachia, 

 where it is basal, and runs into the glenoid cavity. 



