244 Bulletin 47, United States National Museum. 



draw any satisfactory line between Eutilus on the one extreme and Mylo- 

 Icucus at the other. The American species of this genus are very imperfectly 

 known, and some of them are subject to large variations, (rutilus, ruddy, 

 the ancient name of the European Roach or Rothauge, Eutilus rutilus.) 



LF.UCOS, (\u6s, white.): 



a. Teeth 5-5, never 4-5, nor 5-6 ; anal fin short, of about 8 rays ; scales small, sexual differ- 

 ences slight, males with little or no red pigment. 



b. Scales about 58 to 65 in the lateral line. Body slender, the depth 4 in length ; color 



olive, the belly silvery. OLIVACEUS, 385. 



MYLOLEUCUS, (juntos, grinder ; Leucos) : 



oa. Teeth 4-5, with grinding surface ; anal fin short, of about 8 rays ; scales small. Dusky 

 species, the scales sprinkled with dark dots. Sexual differences moderate, usually some 

 red pigment in spring. 



c. Scales in lateral line 45 to 67. 



d. Scales 8-46 to 50-5 ; coloration paler and less dotted with black. 



BICOLOR, 386. 

 dd. Scales 10 to 14-50 to 67-5 to 7 ; coloration dusky, much dusted with dark specks. 



SYMMETRICUS, 387. 



oc. Scales rather large, 39 in lateral line ; about seven rows between lateral line and dor- 

 sal ; sides with a plumbeous baad and a black caudal spot. BOUCARDI, 388. 



Subgenus LEUCOS, Heckel. 

 385. RUTILUS OLIVACEUS (Cope). 



Head 4 ; depth 4$- to 4. D. 8 ; A. 8 ; scales 11-56-6 ; teeth always 5-5, 

 with grinding surface. Body fusiform, compressed ; head narrowed to the 

 muzzle, the mouth opening very obliquely forwards and upwards; maxil- 

 lary concealed in the closed mouth, its tip scarcely reaching front of eye. 

 Eye li in snout, 1| in interorbital space, 5 in head ; middle of front flat, 

 its edges sloping to the superciliary border ; pectoral long, reaching f dis- 

 tance to ventrals. Dusky olive, with brassy luster, the belly silvery; 

 body and fius much dotted ; no red or yellow ; no lateral band ; young 

 with lateral line incomplete. Length 1 foot or more. Lake Tahoe, Pyra- 

 mid Lake, and neighboring waters ; excessively abundant ; much resem- 

 bles Leuciscus lineatus in appearance and habits ; a greedy fish, destruc- 

 tive to young trout, (olivaceus, olive-colored.) 



Leucus olivacem, COPE, Proc. Ac. Nat. Sci. Phila., 1883, 145, Pyramid Lake, Nevada. 



Leucus dimidiatus,* COPE, I. c., 145, Pyramid Lake, Nevada. 



Siphateles viltalusrf COPE, Proc. Ac. Nat. Sci. Phila., 1883, 146, Pyramid Lake, Nevada. 



Subgenus MYLOLEUCUS, Cope. 

 386. RUTILUS BICOLOR (Girard). 



Head 4; depth 4*; eye 4*. D. 8; A. 7; scales 9-48-6; teeth 4-5. Body 

 moderately stout. Head rather heavy, the muzzle short and conical. 

 Mouth moderate, very oblique, the jaws equal, the maxillary reaching 

 line of eye. Scales rather large. Lateral line decurved. Eye rather large. 

 Color transparent olivaceous; a distinct plumbeous lateral band; tins 



*Eye equal to interorbital width, 3% in head, a little more than length of muzzle. Mouth 

 oblique, the maxillary reaching front of eye. Ventral a little behind front of dorsal. Light 

 brown above, becoming plumbeous lower, the belly pure silver white. Head 4 ; depth 4%. A. 8. 

 Scales 14-65-8. Teeth 5-5, with grinding surface. Length 4 inches. Pyramid Lake, Nevada; 

 very abundant. (Cope.) Evidently the half-grown of E. olivaceus. 



fHead 4; depth 4%; eye 3. D. 8 ; A. 8 ; scales 11-55-5; teeth 5-5, with well-developed 

 grinding surface. Lateral line very imperfect. Eye a little less than interorbital width. Mouth 

 oblique, the maxillary not quite reaching front of eye. Ventral fins beneath anterior part of 

 dorsal. Brownish above, belly and sides silvery ; a straight lateral band of lead color, inter- 

 rupted at base of caudal by a vertical baud of straw yellow, which has a dark posterior edge. 

 Length 3 inches. Pyramid Lake, Nevada, evidently the young of E. olicacem. (Cope.) (vittatus, 

 striped.) 



