74 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



This genus, AmpMplaga, and Urismatopterus form a group which 

 probably belongs to the family of Aphrodediridw, which is represented in 

 American waters by the recent genera Aphrodedirus and Sternotremia. 

 The present species, the only one in which the parts are large enough 

 and sufficiently well preserved for observation, exhibits the furcate 

 character of the femora, which characterizes the family in question 

 among Physoclystous fishes. 



Character specijicus. — The scales extend on the cheeks and abdomen; 

 there are nine or ten longitudinal rows above the vertebral column and 

 about sixteen below it. The head is moderately elongate and deep 

 behind. The mouth is subterminal, and the extremity of the premax- 

 illary bone extended backward would reach about half-way to the orbit. 

 Eibs stout; neural spines slender. The interneurals visible number 11, 

 but the posterior part of the dorsal fin is wanting. These bones have 

 thin anterior and posterior laminar expansions. The anterior inter- 

 neural strikes the fifth vertebra from the head ; between this one and 

 the first interhsemal there are nine vertebrae. 



Measurements. 



M. 



Length of head to first vertebra i 0. 028 



Depth of head posteriorly 0.022 



Length of mandibular ramus 0.013 



Length to scapula 0. 035 



Length to dorsal fin 0.050 



Depth at middle of dorsal fin 0.023 



From the Tertiary shale of Florissant, Colorado; discovered by my 

 friend Br. 8. H. Scudder, of Boston, collaborator of the United States 

 Geological Survey of the Territories. 



Prtscacaea oxyprion, sp. nov. 



Five specimens in nearly complete preservation represent this species 

 in our collections. It is more nearly allied to the P. serrata than to the 

 other species, as the spine of the ventral fin is large and robust. It 

 differs from that and from all the other known species of the genus in 

 the small number of the radii of its anal fin. It agrees with P. serrata 

 in the small number of, the rays of the second dorsal. It is a smaller 

 species than the P. serrata, being intermediate in size between it and 

 the P.pealei. It is especially marked by the long, acute serrse of the 

 entire posterior and inferior margins of the preoperculum. The oper- 

 culum, suboperculum, and cheek are scaled ; the preoperculum is naked. 



Formula : Br. YIII ; D. X— 11 ; Y. 1—5 ; A. Ill— 8 ; Vert. D. 10 ; 

 Caud. 14. The form is an elongate oval, rather more elongate than any 

 other species of the genus. The mouth is terminal and the front gently 

 convex and descending. The length of the head enters the total, less 

 the caudal fin, two and a half times, and the greatest depth is half of 

 the same. The dorsal spines are long and strong, the longest equalling 

 the soft rays in length. The anal spines are very robust, the second or 



