m'clung: the Kansas cretaceous. 245 



coid but is a heavy bone bearing three facets for the articula- 

 tion of the fin-rays. Very probably also it contains one or more 

 of the six oval pits for the reception of the baseosts, since the 

 mesocoracoid rises above the first, second and third of these. 

 The fin-ray articulations are quite unlike those of Xiphactinus 

 and Gillicus, being much roughened for the attachment of liga- 

 ments. The entire construction of the girdle would indicate 

 little movement of the fin, which was apparently more or less 

 rigidly braced against the body. The hypocoracoid is a heavy, 

 irregular bone, large dorsally, where it bears some of the pits 

 for the baseosts, and thinner ventrally. It is flattened in a 

 cephalocaudal direction at right angles to the plane of com- 

 pression in the clavicle. In the specimen from which figure 10 

 was drawn the ventral portion shows a roughened edge, proba- 

 bly indicating the presence of another element. 



It is evident from the construction of the girdle that the 

 diff'erences are considerable between Protosphyrsena and the 

 other genera considered here, and lend further justification to 

 the classification which places it in a group by itself. 

 caudal fin of protosphyr^na. 



The entire skeleton of any member of this genus has not yet 

 been discovered. There is therefore lacking a knowledge of 

 several portions of the body, among which are the occipital 

 region of the skull, the vertebral column and the caudal fin. 

 Light upon all these points is afforded by material now at my 

 disposal. I wish here to consider the caudal fin and incidentally 

 the vertebrae. Through purchase from Mr. C. H. Sternberg 

 the University of Kansas has come into possession of a speci- 

 men of the caudal fin, which not only shows the nature of this 

 organ but also clearly demonstrates the absence of ossified 

 vertebrae. In plate XIII is represented a lateral view of this 

 specimen, from which the essential features may be understood 

 without much description. The ossified neurals and haemals 

 appear very plainly, as they do in the nearly related Hyposocor- 

 mus, according to Woodward, but the centra are absent. The 

 last haemal is considerably modified, forming a urostyle, to 

 which many of the fin-rays attach. This bone is frequently 

 found by collectors, but its character and relationships have 

 not heretofore been understood. The fin-rays are fine, closely 

 apposed and very numerous. In the specimen under considera- 

 tion they are incomplete and broken, so that the exact form of 



