ON TWO NEW FORMS OF POLYODONT AND GONOEHYNCHID FISHES FROM 

 THE EOCENE OF THE ROCKY MOUNTAINS. 



HEAD NOVEMBER 12, 1885. 



By E. D. Cope. 



CROSSOrnOLIS MAGNICAUDATUS Copo, American Naturalist, 1883, p. 1152; ' loc. cit., 1885, p. 1000. 



Since tbe description of tbe part of tlio body of tbis fisb was publisbed, I bave obtained a 

 considerable ])ortion of tlie skull of au individual of tbe same genus, if not species. It belonjjs 

 ai)parently to a lavi^er individual tbau tbe one first described. Altbougb it was found at tbe same 

 locality .as tbe latter, and at near tbe same time, it is not part of tbe same individual. Tbe cbar- 

 acters of tbe family Polyodontidce are easily discerned in tbe skull, and tbose of tbe body coincide. 



Tbe sknil displays typical ordinal and family cbaracters. Tbe postempoia! bone is produced 

 backwards, and is separated froui tbe parietal by a large foramen, wbicb continues between tbe 

 dermospbenotic and parietal. It is bounded in front by a i)rocess of tlie dermospbenotic, wbicb 

 joins a correspondinn: one from tbe frontal. Anterior to tbis connecting bridge, anotber large fora- 

 men extends, separating tbe derinos])benotic and an element continuous wiili it anteriorly, pcrbaps 

 a brancb of tbe nasal, (rom tbe frontal. Tbe maxillary and mandibular bones occujiy tbeir usual 

 position; and tbe byomandibular extends posteriorly from near tbe junction of tbe jiterotic and 

 tbe epiotic. Tbe eiiiclaviclet is simjile, and tbe oi)erculum arises from near tlie distal end of tlio 

 byomandibular. Immediately below its anterior portion is a flat element, wbicb does not occur 

 apparently in Polyodon. It may be preojjerculum or suboperculum, or tbe interoperculum of 

 Polyodon in a different position. 



Interneural and interbremal basilar bones are large and are ossified, and tbe caudal baiina- 

 po]d)yses ("liypurals") are but little less so. Tbe caudal fin is entirely beterocercal. Vertebral 

 axis consisting of notocbord only. 



Char. (jen. — Tlie bone in tbe position of preoperculum above mentioned, is in contact witb tbe 

 inferior face of tbe superoanterior extremity of tbe operculum by its superior extremity. Its an- 

 terior border is entire, snbvertical, and convex. Its posterior edge is not preserved, but tbe impres- 

 sion of its external surface is deeply grooved, as tbougb tbe bone were ridged anteroposttrioily. 

 Tbere are i)reserved several loose tbin plates of bone covered witb small teetb en brosse, wbicb 

 bave come from tbe premaxillary and dentary bones. Tbere are preserved a number of stellate 

 bones of tbe muzzle. 



Scales numerous, in oblique series, not in contact, formed of a small grooved disk and several 

 posterior spines. Dorsal and anal fins sbort, posterior; tbe former commencing in advance of tbe 

 latter. Caudal fulcra posteriorly slender, continued into broad flat scuta extending forwards on tbe 

 median line of tbe caudal peduncle. Superior lobe of caudal fin mucb more produced tbau inferior. 

 A lateral Hue of tubules. 



" By a typographical error, Crassopholis at this reference. 



tl employ the uouienclature of Bridge in liis paper on the Osteology of Polyodon folium, Pliilosojih. Transac. Eoyal 

 Society, 1878, p. 688. 



S. Mis. 154 21 161 



