I903-] 



Hay, North American Cretaceous Fishes. 



1 1 



smaller ridges and at length disappears. Those of the distal 

 portion of the fin may be traced nearly across the fm. 



A considerable part of the shoulder girdle of the fin above 

 described is present (Figs. 4, 5), and it. enables me to make 

 some corrections in Cope's account of this part of the anatomy 

 (Vert. Cret. Form. West, p. 244A). This author affirmed 

 that all the basilar bones, which support the fin, articulated 

 with the scapula ; and on this character he founded the order 

 Actinochiri. 



Fig. 4. Protosphymna perniciosa (Cope), Fig. 5. Protosphyrcena perniciosa(^Q,o^€), 

 No. 1901. X 3. t/., cleithrum ; cor., coracoid ; No. 1901. X 3. cl., cleithrum ; cor.., cora- 

 sc, scapula. coid ; /. tvjr., precoracoid. 



The conclusion reached by Cope is obviously erroneous ; for 

 it is certain that the greater portion of the bone which he 

 identified as the scapula is the coracoid; while the bone sup- 

 posed by him to be the coracoid is the precoracoid. The 

 result of his erroneous determinations was that he had the 

 shoulder girdle turned wrong end up. All this is satisfac- 

 torily proved by comparing these bones with the correspond- 

 ing ones of Tarpon or Salmo. Unfortunately, most of the 

 sutures in this complex of bones are obsolete, and Cope him- 

 self was unable to make them out in his specimens. At the 

 base of the precoracoid of No. 1901 there is a dislocation of 

 the latter which may indicate the position of the suture. In 

 the tarpon the enlarged anterior fin ray and two baseosts 

 articulate with the scapula. In the specimens of Proto- 

 sphyrcBna there are no satisfactory indications of the suture 

 that once existed between the scapula and coracoid. 



