M'CLUNG: THE KANSAS CRETACEOUS. 241 



or less completely. The largest of these is the clavicle, which 

 only slightly exceeds in size the hypocoracoid. Between these 

 elements is placed the heavy hyper- and intercoracoids, the 

 former bearing the facets for articulation with the fin-rays. 

 The dorsal portion of the hypercoracoid is joined by a heavy 

 suture to the ventral border of the vertical limb of the clavicle. 

 Beyond this point, as was noticed in the description of the 

 caudal view, a thin plate extends dorsally between the clavicle 

 and mesocoracoid. The inner ventral margin, at the level of 

 the lower and middle facets, is joined to the inter- and meso- 

 coracoids. 



Except for a heavy process arising from the outer surface 

 to join the ventral edge of the intercoracoid, the hypocoracoid 

 is a thin, fragile bone which is nearly always broken at the 

 edges. From a number of specimens the various parts of this 

 edge have been observed and from them the restoration in plate 

 XI made. Just in front of the suture joining this bone to the 

 hypercoracoids is an oval foramen piercing the hypocoracoid. 

 This was described as absent by Hay ('98, p. 43). Sometimes 

 there are several of these. Ventral to this are two stout pro- 

 cesses running forward, approximately parallel. These join 

 the stout dorsocaudal process of the hypocoracoid to its thin 

 inner plate. Elsewhere these are separate. Aside from these 

 diversities the bone is uniformly thin, except at the dorsal edge, 

 where it thickens strongly to join the hyper- and mesocora- 

 coids. 



The clavicle has been well figured and described except that 

 usually it has been represented as too narrow dorsally. But so 

 far as I have been able to discover there has been no record of 

 the supraclavicle that attaches to the dorsal edge of the clavicle. 

 This is the "uncertain bone" shown by Stewart (figure 2, 

 plate 44) . A portion of it is attached to the girdle from which 

 Stewart's figure 1, plate 45a, was made, but it does not appear 

 in the drawing. In a number of specimens it can be seen, on 

 the inner side, attaching firmly to the caudal margin of the 

 dorsally projecting process of the clavicle, and, by means of a 

 thickened ridge, to the angle which this clavicular process 

 makes in descending to join the dorsal edge of the mesocora- 

 coid. Upon the inner surface of the thin, caudal portion of the 

 clavicle it becomes much attenuated and gradually thins out. 

 It does not anywhere come into relation with the mesocoracoid. 

 (See figures 1 and 6.) 



