NO. 2177. FOSSIL FISHES TN NATIONAL MUSEUM— EASTMAN. 295 



longus is only a young example of this fomi, the individuals of which 

 show a considerable amount of variation. In plate 21 is shown a 

 large (44 cm. long) and well-preserved specimen v/hich may be referred 

 to M. lahracoides, notwithstanding the fact that it displays one 

 abdominal and one caudal vertebra in excess of the normal number 

 occun-ing in the type-species. The type of M. multidentatus Cope has 

 not been figured. It is preserved in the American Museum of Natural 

 History. 



Formation and locality .—Gveen River Eocene; Wyoming. 



Genus PLIOPLARCHUS Cope. 



This extinct genus, closely related to Miophsus, is represented by 

 three Lower Tertiary species, of which only one, P. wliitei Cope, has 

 been iUustrated. The differences between this species, which is the 

 type, and P. sexspinosus, are stated to consist in the more numerous 

 spinous, and less numerous soft rays, of the dorsal and anal fins. In 

 P. whitei the radial formula is: 



D. IX-12; C.-17-; A. V-14; V. ?; P. 13. 

 And in P. sexpinosus it is: 



D. X-13; C. -17-; A. VI-9. 

 In P. septemspinosus the formula is given as: 

 D. XI-?; A. VII (?)-12. 



PLIOPLARCHUS SEXSPINOSUS Cope. 



Plate 15, fig. 1. 



Plioplarchus sexspinosus Cope, Amer. Joiirn. Sci., vol. 25, 1883, p. 416; Rept. 

 U. S. Geol. Surv. Terr., vol. 3, 1884, p. 729. 



In the original description it is stated that "this species is repre- 

 sented by two specimens, both of which lack the head and body an- 

 terior to the dorsal fin." These specimens are now in the United 

 States National Museum collection, and one of them, marked "type," 

 is catalogued as No. 4236. It is from the Lower Tertiary, perhaps 

 Miocene, near Sentinel Butte, in Billmgs County, North Dakota. A 

 much more complete example, also from the type locality, is shown 

 in our plate 15, figure 1. In it the anal fin is seen to have six spinous 

 and twelve soft rays. The specimen bears the catalogue number 8118. 



Formation and locality .—Miocene ( ?) ; top of Sentinel Butte, North 

 Dakota. 



PLIOPLARCHUS SEPTEMSPINOSUS Cope. 



Plate 22. 

 Plioplarchus septemspinoms Cope, Amer. Naturalist, vol. 23, 1889, p. 625. 

 This species was established by Cope upon the evidence of four 

 distorted and mutilated specimens from shales near Van Horn's 

 ranch, on the John Day River, Oregon, the strata whence they were 



