94 FOSSIL REPTILIA OF THE 



exhibits a stronger tuberosity near the same part ; the sternal end of this bone is 

 slightly expanded and rounded. The length of the scapula is rather more than one- 

 third of that of the entire skull. 



In the same block of chalk as that which contained the fore part of the jaws of 

 the Pt. giganteus, is preserved the confluent extremities of the right scapula and 

 coracoid, one third larger than the corresponding parts in the Pi. crassirostris, and 

 one-fourth larger than those in the Pt. macronyx. The portion of scapula, (T. XXXI, 

 figs. 7 and 8, 51,) includes thirteen lines of the humeral end of that bone ; the fractured 

 part of the body showing that part to be subcompressed, with the side next the ribs 

 slightly concave, the opposite side convex ; the long diameter of this section of the 

 bone is 3 lines ; its short diameter 1 line ; it expands as it approaches the shoulder 

 joint, and developes an obtuse oval tubercle, a, from its upper and inner border about 

 4 lines from the articular end ; a low acromial ridge is extended from the outer side 

 of the bone, from near the origin of the tubercle, to the outer and fore part of the 

 glenoid cavity : the inner and posterior border is expanded into a third ridge which 

 joins a corresponding one from the same part of the coracoid, Of this bone, 52, about 

 ten lines is preserved : the transverse section exposed at the fractured end is oval, 

 and measures 3^ lines by 2 lines ; the expansion of the bone to form the shoulder- 

 joint is rapid. Besides the ridge sent off from the inner and back part to join the 

 one above mentioned from the scapula, there is a much stronger process, c, developed 

 from the under and fore part of the coracoid, as in that of the Pt. macronyx, between 

 which and the glenoid surface the bone is perforated by a narrow canal, the inner 

 outlet of which is just above the inner ridge. If we carry forwards the two straight 

 lines respectively parallel with the outer borders of the scapula and coracoid, they will 

 meet at an angle somewhat less acute than those in the Pt. macronyx. By a trace of 

 the original suture we may see that the coracoid has formed about two thirds of the 

 glenoid cavity, (fig. 7, g .) the long diameter of that cavity measures 6 lines, its short 

 diameter 3-g- lines ; in the direction of which it is flat above and slightly convex 

 below ; being concave only in the direction of its long axis ; its contour is reniform, 

 the convex border being extended upon the acromial ridge. The long diameter of the 

 glenoid cavity in the Pt. macronyx measures 4 lines ; and the absence of the 

 tuberosity on the scapula makes that end of the bone relatively more feeble than 

 in the present instance. As the parts are fully one third larger than those in the 

 Pt. crassirostris, we may estimate the skull of the present species according to the pro- 

 portions of the scapula to the skull in Pt. crassirostris, as having been about 7 inches 

 in length. Both the scapula and coracoid are hollow, the cavity being surrounded 

 by a very thin compact wall, and being subdivided by a few much thinner plates. 



There is a fragment of a bone, (T. XXXI, fig. 9,) in the same block of chalk, 

 which, from its rapid expansion, I am induced to suspect to be part of the sternum: 

 its thickest part presents a coarse cancellous structure : from this part it expands 

 into a thin plate, of which, however, not enough remains to indicate its original form. 



