88 THE WASATCH AND BEmOER FAUN^. 



MIOPLOSUS Cope. 



BnUetin U. S. GeoL Surv. Terra., 1877, p. 813. 



Allied to Labrax and Perca Branchiostegal rays, 7 or 8 ; ventral 

 rays, I. 5 ; scales ctenoid. Two dorsal fins slightly connected at base ; 

 only two anal spines. Operculum rounded, without spines or emargination. 

 Preoperculum without spine, and smooth on the posterior border ; inferior 

 border with teeth. Premaxillary and dentary with small uniform teeth in 

 a narrow series. Clavicle unarmed. Vertebrae with two lateral fossae. 

 Caudal fin emarginate. 



The discovery of this genus in the Green River shales is of no small 

 importance to fossil ichthyology, proving the existence, at that early period, 

 of the type which is one of the highest among the true fishes. It probably 

 beloi:g8 to the Percid^B, although I have not ascertained the presence of 

 teeth on the vomer, and there may be eight branchiostegal rays. As 

 compared with the genera, recent and extinct, which are allied to Perca, it 

 differs in the unarmed operculum, and the preoperculum with teeth only on 

 the lower limb, and in the presence of but two anal spines It is therefore 

 a weaker form than they, and though of a higher type, less strongly 

 protected by spines than the cotemporary Asineops. Mioplosus embraces 

 the largest Physoclystous fishes yet known from this formation, and speci- 

 mens are not rare at the locality from which they have been procured. 

 They are often in a state of excellent preservation. The type of the genus 

 is the M. lahracoides. 



MlOPLCSUS ABBREVIATUS CopC. 

 Bulletin U. S. G«ol. Surv. Terra., 1877, p. 814. 



The M. abbreviatus is represented by but one specimen, from which 

 the muzzle has been broken away. It is the stout species of the genus, and 

 the others succeed it in this enumeration in the order of their greater elon- 

 gation of form. The depth at the first dorsal fin enters the total length 

 (including caudal fin) three and a half times ; and the depth at the first 

 anal ray enters the length of the vertebral column two and eight-tenths 

 times. Vertebrae visible behind clavicle: D. 9 ; C. 14. Radii: D. IX — L 



