66 SHOULDER-GIRDLE AND BREAST-BONE. 



In Plate IV, figs. 8 and 10, the parts of an old specimen are given, magnified four diameters ; 

 fig. 8 showing the left and part of the right Shoulder-plate, whilst the same parts are seen from 

 behind in fig. 10. The former figure shows the complete fusion of all the bones, and the more 

 pointed prse-coracoid (p. cr.) ; and the latter displays the ucetabuliform glenoid cavity, and the 

 thickness of the plate in its various regions ; they both show what is worthy of remark, namely, 

 that whilst in those shown in figs. 6 and 9 the left epicoracoid lay beneath the right, the right 

 underlay the left in this aged individual. 



In remarking upon fig. 8, besides the rich development of solid cartilage, let us notice 

 that the angle between the scapula and prse-coracoid (sc., p.cr.) is not filled in by perichondrial 

 bone. Plate IV, fig. 11, shows a section of the Sternum from side to side, and magnified ten 

 diameters ; it is much thinner than in the Newts, and is invested with a loose perichondrium 

 passing insensibly into the pericardium. The letters st. are placed where the heart lay ; the 

 right side of the figure being the cutaneous surface. 



"AMPHIBIA ANOURA." 



Were it not for the Caducibranchiate Urodela the Salamandrinse, the gap between the 

 Urodelous and Anourous types of Amphibians would be a large one ; in reality it is not so 

 narrow as might be supposed, for the difference between the two is wellnigh equal to that which 

 is found between the Heterocercal and Homocercal Pishes ; and like that which we have at last 

 come to see between the ArcJueopteryx and the typical Bird. Besides the rapid absorption 

 and modification of the large series of caudal vertebrae in the Anoura, we have a sudden and 

 rather surprising development of the limbs ; and it is not to be passed over without remark that, 

 as quadrupeds, although the " heavy-gaited Toad lies in " your " way," sluggish and languid, 

 yet the highest type the Prog, a Locust among the Vertebrates, has no compeer, gymnastically, 

 until we come to the Kangaroo and the Beaver ; and, although ichthyic in his essential nature, 

 in activity he is at once a rival to both these athletes. 



Consonant with the sudden activity of the Anourans we have remarkable changes in the 

 structure of the Limb-girdles, and also of the Sternum ; but the ribs are still abortive, and a large 

 space exists in the side-walls of the thorax, unguarded by bone or cartilage (a correlation this, 

 beautiful enough, with the extreme fecundity of these creatures), whilst in apposition with the 

 huge, elastic, mobile Shoulder-girdle, a considerable Sternum crops out in the lower part of the 

 thoracico-abdominal walls. In the Anoura a higher degree of segmentation is combined with 

 a fuller ossification ; and one new bony element, the " supra-scapula," developed by two kinds of 

 ostosis, appears in every known species. 



In all the known Urodela the endosteal deposits are entirely ruled by the much earlier and 

 more potent ectosteal sheath ; in the Anoura this state of things is rare, (for instance, in 

 Pelobates) ; but as a rule the two processes are independent of each other : the two deposits 

 of bony matter often continue distinct throughout life. The Anoura cannot trace their descent 

 from one ichthyic fatherhood ; for in them is combined the histological and morphological 

 characters of the Plagiostomous Shark and Ray on one hand, and the Sturgeon and the 



