586 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



and branchiostegal radii are wide and thin-edged. All the bones of the 

 head are marked by parallel or radiating ridges, which radiate from the 

 point of attachment to the free border, or from the center to the cir- 

 cumference, in the case of the superior cranial bones. In the maxillary 

 bone, the radii extend parallel from the anterior margin horizontally 

 backward. 



The vomerine patch extends almost entirely across the roof of the 

 mouth. The orbit is longitudinally oval ; its long diameter entering the 

 cranium five and a half times, and the part of the same in advance 

 of it one and a half times. The orbit enters the iuterorbital width two 

 and a half times. The length of the head enters the depth of the 

 body one and one-quarter times. The pectoral fin is acuminate in form, 

 and, being laid against the fish's side, passes above the vertebral 

 column for the greater part of its length, reaching the line of the nine- 

 teenth vertebra which is visible from the line of the scapular arch. 

 It has 15 or 16 rays, the first stout, curved, and segmented at the ex- 

 tremity. The number of anal radii is uncertain, but not large. The 

 ventrals are imperfect, and reach to the base of the anal. The caudal 

 fin had a narrow peduncle, and expands abruptly from the base. 



The vertebral column is interrupted by a fracture, but it is probable 

 that few, if any, vertebrae are lost at the break. If this be true, there are 

 thirty-four vertebne between the scapular arch and the first chevron- 

 bone, all of which bear long subequal ribs. The centra are rough with 

 rather irregular longitudinal strice. The scales are badly preserved ; 

 where visible, they are thin, without sculpture, and not small. About 

 twelve longitudinal series intervened between the vertebral column and 

 the base of the dorsal fin, and six or eight rows extended along the 



caudal peduncle. 



Ileasiirements. 



M. 



Leugtli of head 0. 227 



Length of body to first caudal vertebra (with a break) 0. 390 



Depth at scapular arch h 0. 230 



Depth at anal fin 0. 265 



Depth at caudal peduncle 0. 055 



Depth of skull at superciliary border 0. 080 



Width of skull at superciliary border ^ 0. 110 



Leugth of x^ostorbital bones 0. 045 



Width of border of premaxillary bone 0. 055 



Length of pectoral fin 0.210 



Vertical diameter of a dorsal scale 0. 010 



Longitudinal diameter of free part of the same 0. 009 



3. — VERTEBRATA FROM THE FORT PIERRE FORMATION. 



PELYCORAPIS Cope. 



Report U. S. Geol. Surv. Terrs., ii, p. 182. 



This genus of fishes is one of the type so common in the Cretaceous 

 formation, which present a combination of Physostomous and Physo- 



