284 University Geological Survey of Kansas. 



There is a great variation in the size of the various specimens, 

 and the measurements given are below the average, this speci- 

 men being selected on account of its completeness. 



Clei thrum : Length from scapula superiorly 233 mm. 



Length from scapula anteriorly 230 " 



Precoracoid : Length 190 " 



Numerous fragments of fins and fin-spines are present, which 

 show that these formed powerful weapons of defense ; they have 

 been described by Crook as resembling ribs. The first pair of 

 these are closely applied to each other and are each provided 

 with articular surfaces at the proximal extremity, the first of 

 which articulates directly with the upper condyle of the scapula 

 while the second articulates with one of the basiosts. The first 

 of these is broad and thin, while the second is slightly narrower 

 but thicker toward the proximal end. The two opposing sur- 

 faces are much roughened while the outer surfaces are finely 

 striated. The following rays decrease greatly in width and are 

 much smaller from above downward. They are slightly bent 

 at the proximal extremities and the cross-segmented character 

 has disappeared throughout. The basiosts are three in 

 number. The first of these is an irregular-shaped bone which 

 is provided with two facets internally for articulating it with 

 the two lower condyles of the scapula. These two are some- 

 what oval in outline, flat, and well separated from each other. 

 The external facets are also two in number, one of which is 

 nearly circular in outline and flat, while the other is irregular 

 and strongly convex from above downward. The two remain- 

 ing basiosts are somewhat thickened bars of bone which are 

 slightly expanded at the extremities and are provided with con- 

 vex condyles, the proximal ones of which are received into the 

 pits on the coracoid and scapula for their reception. About 

 midway between the extremities of each of these basiosts there 

 is a thin transverse process extending outward. 



The pelvic actinosts, called femora by Professor Cope, 49 con- 

 sist of two parts — a massive posterior portion, bearing the 

 facets for the attachment of the pectoral fin, and the thin, 



49. Cret. Vert. West., p. 186. 



