AMPHIBIANS. 61 



In fig. 2 the glenoid fenestra is not seen it lies in shade, but it can be seen in fig. 3 ; it is 

 quadrilobate. The Sternum (st.) is two-thirds the size of the coraco-epicoracoid plate, and is very 

 unsymmetrical ; this arises from its relation to the overlapping epicoracoid. In the figure it is 

 shown as drawn away from these flaps, but they, in certain positions of the living creature, 

 reach to the oblique, thick ridges on the inside of the sternum ; anterior to these ridges the 

 unequal, thin, sinuous, lower coracoid lips are seen, which are out-growths of the pri- 

 mordial part of the Sternum, and which underlie the epicoracoids. The antero-lateral 

 margins are notched (sinuously) twice ; the posterior margin is deeply bilobate, and near the 

 emargination there is a foramen not an uncommon thing in the Sternum of the Urodelous 

 Amphibians. 



Example 5. Siredon pisciformis, Shaw. 1 



The Axolotl's Shoulder-girdle and Sternum are shown in Plate VIII, fig. 1, three times the 

 natural size; they are from fresh dissections, and are shown as somewhat outspread for the sake of 

 diagrammatical accuracy. The fan-shaped supra-scapula (s. sc.) has a constriction below, showing 

 the commencement of the true scapular region, left untouched by the arrested shaft-bone. The 

 scapula (sc.) is oblong, with slightly sinuous sides, flat, and rather dilated below, not reaching quite 

 to the middle of the glenoid excavation, which is triangular and thick-lipped : it is not fenestrate 

 within, but is carved out of thick cartilage. There are two nerve-passages, a line apart, on the 

 left side, showing that they are not a very accurate landmark, but useful, nevertheless. The 

 prse-coracoid (p. cr.) is narrow, oblong, short, and slightly emarginate at its free end ; the notch is 

 cut out in a rounded manner, and its lower boundary, or outline of the epicoracoid (e. cr,), is wavy. 

 For the rest, the main coracoid lamina is large, oblong, squarish behind, and rounded in front ; 

 its posterior angle is rather acute and produced, like what is seen in all the higher Ovipara. 

 The left moiety underlies the right, and, in an undisturbed state, the large free edges of the 

 Sternum underlie both ; the epicoracoid edges abutting against the thick inner coracoid lips the 

 earliest part of the Sternum. This is the most symmetrical Sternum to be seen amongst the 

 Urodela, but it is emarginate behind, and only represents the " manubrium." The decussating 

 lines, showing where the great pectoral muscles crossed each other, are well seen ; but there is no 

 ridge for the recti aldominis the Sternum is concave in this part, at the mid-line. The heart 

 lies on the Sternum as on a shallow dish, and the connective fibres forming the pleural lining of 

 the thorax, and those that form the pericardium, and the perichondrial investment of the inner 

 face of the Sternum, are badlv differentiated. 



B. With two Ossifications in each moiety of the Shoulder-girdle. 

 Example 1. Siren lacertina, Linn. 

 My figure of the right moiety of the Shoulder-girdle of the Siren (Plate III, fig. 5) is shown, 



1 The Axolotl, as I have learned since the above was written, is merely a large arrested 

 larva of the American Salamander (Amblystoma) : only a minority of individual Axolotls undergo 

 metamorphosis. 



