FAUNA OF THE GOSATJ FORMATION. 



697 



is, unfortunately, not preserved ; and the plate is remarkably con- 

 vex from before backwards above, though this convexity is more 

 marked on what I take to be the posterior side than on the anterior 

 side. The extreme width of the plate below the articular head of 

 the rib is about 13J centim. ; and it gradually tapers as it extends 

 outwards. Distally the thickness of plate and rib diminish ; and at 

 the extreme distal end, where the transverse measurement, as pre- 

 served, is under 3 centim., the thickness of the combined plate and 

 rib is less than a centimetre. The posterior half of the plate, while 

 smoother externally than the anterior half, is marked with several 

 short, parallel, straight, vascular grooves, which are very narrow ; 

 each is about 2 centim. long. This condition leads me to suspect 

 that the anterior part of the rib may have been imbedded in muscle, 

 while, owing to its curvature, the middle of the plate may have had 

 only a dermal covering. 



The interior or under side of the specimen has the expanded head 

 of the rib broken away ; and while it was placed in the middle of 

 the width of the plate as in the other specimen, the rib soon be- 

 comes developed on the anterior border, being limited by a concavity 

 which runs down the length of the bone, dying away with the ele- 

 vation of the rib at the distal end. This principal part of the rib 

 becomes narrower as it extends further outward ; but the fractured 

 condition of the posterior margin appears to indicate that the margin 

 of the rib was prolonged as a thin film towards the adjacent plate. 



No similar remains which are referable to an animal of this kind 

 have been discovered. 



Scapula of large Chelonian. 



The fragment which I identify as a portion of a right Chelonian 

 scapula, indicates an animal of somewhat large size. It shows no 

 trace either of the prascoracoid or the articular end of the bone, which 

 had decomposed prior to fossilization, or of the distal end ; so that it 

 is not a fragment giving valuable information concerning the affini- 

 ties of the animal. The fragment is 9 centim. long, 4 centim. 

 wide at the proximal end, as preserved, and 2 centim. wide at the 

 distal end. The surface which I take to be posterior is smooth, 

 convex from side to side, but more flattened at the distal end than 

 at the wider proximal end. In length the surface is almost straight. 

 The internal margin is concave and sharp, and looks as though it 

 might have been produced into a prsecoracoid. The external margin 

 is slightly convex, except towards the proximal end, where it is 

 modified, owing to the bone bending outwards and downwards, as 

 though for the formation of the articular surface. The anterior 

 aspect of the bone is much rougher ; and there is a ridge which 

 becomes stronger towards the proximal end, thickening the bone 

 on its outer part, and making it concave in length, and dividing the 

 anterior aspect into a broad, flattened, inner area and a narrower 

 external area. The thickness of the bone towards the proximal end, 

 where fractured, is 2 centim., and the thickness towards the distal 



