AMPHIBIANS. 77 



posterior bar forms almost half the glenoid cavity (fig. 3). In this figure the prse-eoracoid (p. cr.) 

 is foreshortened ; but in fig. 2 it is well shown, and is like a serpent's fang, only much 

 more grooved. This groove receives the endosteal cartilage, which, as a broad band, overlap- 

 ping its fellow (the left over the right), passes from the pra3-coracoid to the coracoid. This 

 latter bone (cr.) is, as usual, perfect, is not over thick, and has quite the shape of an ordinary 

 phalangeal bone. 



The fenestra (cr. f.) is of an elegant tear-shape, and is directed transversely, the small end 

 outwards. The Sternum (st.) is composed of two parts ; first, an hour-glass-shaped, but flattened 

 prse-mesosternal shaft, and then of a transversely directed xiphi-sternum, which is somewhat 

 two-leaved, has an endosteal body and soft margin, and has its angles turned forwards as in 

 Bufo affua and Hylcedactylus ; but it is more elegant than either of these. 



But this typical Ranine Sternum is not combined with a typical " omo-sternum," for this 

 structure (o. st.) has no outer bone ; and yet, true to its primarily symmetrical nature, it has two 

 delicate endosteal deposits : its shape is not that of a short, but a long spatula. (See it as com- 

 pared with that of Acrudytes, Plate VII, fig. 1, o. st.) 



Example 2. Pleurodema Bibronii, Tschudi. 



Plate VII, fig. 5 shows the Shoulder-bones in this Chilian type, magnified four diameters ; 

 the subject was a young female. 



Referring at once to the keystone of the Shoulder-girdle, the " omo-sternum " (o. st.), we 

 see, as compared with the last instance, and with figs. 1 and 7 (o. st.) of Plate VI, how varied 

 are the footprints of the same morphological power or force. Here (Plate VII, fig, 5, o. st.) the 

 symmetrical, segmented cartilages have been converted into one spoon-shaped flap, with a narrow, 

 sub-cylindrical handle, and a nearly circular, flattened bowl. The handle is a true phalangoid 

 shaft, and the bowl a broad epipliysis ; but these, at their junction, are sealed with the impress 

 of their primordial symmetry by a neatly circular " fenestra." 



Referring at once to the Sternum (st., x. st.), we find that the rounded prae-sternal end has, 

 like most of the xiphisternal, undergone endostosis ; but the hinder half of the pras-sternal region 

 and all the meso-sternum, form together one flattened ray, which is but little pinched at the sides. 

 The two halves of the xiphisternum are joined by a proximal isthmus for more than one third of 

 their extent, and the primordial notch is at first rather narrow, and then suddenly widens. 



The supra-scapula (s. sc.) has sinuous sides, and the upper end not much wider than the 

 lower ; the ectosteal sheath is almost symmetrical ; and the inner margin of its forks bounds a 

 subtriangular lobate space of intercellular bone. The scapula (sc.), the prse-coracoid (p. cr.), 

 and the coracoid (cr.) are nearly like those of the last instance ; but the last two bones are wider 

 apart, the fenestra (cr. f.) being broader, whilst the elongated epicoracoids (e. cr.) do not overlap 

 so much. This is a perfectly typical species ; the Shoulder-structures, altogether, having four 

 pairs of symmetrical and two azygous shafts (diaphyses). 



Example 3. Plectropus pictus, Edyoux. 



Plate VII, fig. 7 shows the lower part of the Shoulder-plates (from above) of a young 

 female of this species from Bengal, magnified six diameters. Here all the outer bones are present, 



