1903-] 



Hay, North Americati Cretaceous Fishes. 



beak are broader than high; but the posterior portion has 

 suffered some distortion. The right vomerine tooth has been 

 functional, but there is hardly a vestige of even the alveolus 

 of the other fang. 



Reference must be made here to a species of this genus 

 which has been described by Dr. Loomis {op. cit., p. 225, pi. 

 XX, figs. 1-4) under the name P. obliquidens. The beak of 

 this is described as being compressed. The author has fig- 

 ured a portion of the pectoral fin; and this appears to agree 

 in every respect with that of our No. 21 21. There is the 

 same front edge, without serrations or undulations; and a 

 band along this edge is represented as being ornamented with 

 fine enamel ridges which run at right angles with the edge. 

 It appears to the present writer that these pectoral fins must 

 be identified as belonging to the same species. Too much 

 importance must not be attributed to the compressed or de- 

 pressed form of the beak. Many of them have been modified 

 by pressure, and there was probably a good deal of individual 

 variation. 



The premaxilla of No. 21 21 is missing. The anterior end of 

 the dentary and that of the splenial are well preserved and 

 are figured (Fig. 3). These 



are attached to the frag- 

 ment of the fin. 'Between 

 these bones and the cor- 

 responding ones of P. 

 obliqtiidens I find no dif- 

 ferences that appear to be 

 important. Dr. Loomis 

 states that his species 

 has three rows of small 

 teeth on the splenial ; but 

 in some cases there may 

 be one row on a portion 

 of the splenial and more 

 than one row in another part. The number of rows of these 

 small teeth is probably not a constant character. The small 

 teeth of the dentary are directed forward, as they are in P. 



Fig. 3. Protosphyrcena nitida (Cope). No. 2121. 

 X J. den., dentary ; /(T^., fragment of pectoral fin; 



j//., splenial. 



