14 Bulletin Atnerican Museum of Natural History. [Vol, XIX, 



which the rays make with the anterior border being the same 

 in both species. Under P . tenuis mention is made of fins 

 whose edges are not repand, but have the summits of the 

 waves sharp. No. 2044 is a specimen which is evidently to 

 be referred to P. perniciosa, since it has the serrations well 

 developed on many parts of the edge. And yet, well out 

 toward the distal end these serrations subside and the edge 

 is nearly straight. It seems possible that there was con- 

 siderable variation in the degree of development of the 

 serrations in different individuals. Only more and better 

 materials will enable us to settle this point. 



Protosphyraena tenuis Loomis. 



Plate I, Figs. 2 and 3. 



Pelecopterus perniciosus Cope (E. D.), Vert. Cret. Form. West, 1875, 



pi. xliv, fig. 13 (erroneous identification). 

 Protosphyr(sna tenuis hoouis (F. B.), Palaeontogr. XLVI, 1900, p. 226, 

 pi. XX, figs. 5-7. — Hay (O. P.), Bibliog. and Cat. Foss. Vert. N. A. 

 1902, p. 379. 

 Protosphyrcsna penetrans Stewart (A.), Univ. Geol. Surv. Kansas, VI, 

 1900, pp. 370, 402, pi. Ixiii, figs. 1—3. 



This species is said to be based on three individuals which 

 were collected by Mr. C. H. Sternberg in the Niobrara de- 

 posits of Kansas and are now in the Museum at Munich, 

 Germany. The parts figured belong to one individual and 

 consist of a rostrum, premaxilla and maxilla of the left side, 

 and a part of one pectoral fin. This appears to be a well 

 founded species. The rostrum is, relatively to the length of 

 the maxilla, very long and slender. The maxilla enters into 

 the length of the rostrum two times, while in a specimen of 

 P. nitida the maxilla is contained in the rostrum only one 

 and a half times. The teeth of the maxilla appear to be 

 smaller than they are in P. nitida. The most certain evi- 

 dence that this species does not belong to P. nitida is to be 

 found in the pectoral fin blade. On comparing it with the 

 figure of Dr. Loomis's P. obliquideiis (= P. nitida), figured on 

 the same plate, we find that in the latter the edge of the fin 

 is devoid of any undulations and that the rays make an angle 

 of nearly 10° with the edge; while in P. tenuis the edge is 



