144 NORTHERN FISHES 



30. Intestine greatly elongated, much coiled on right side 



(Genus Ilybognathu.s) 31 



Intestine short, S-shaped 32 



31. Dorsal fin rounded; color brassy; scales with focus less eccentric, and with 

 about 20 radii in adult 



Brassy Minnow, Ilyhognathus hankinsoni Hubbs 



Dorsal fin somewhat falcate; color silvery; scales with focus very near basal 

 edge, and with about 10 radii in adult 



Western Silvery Minnow, Hyhognathus nuchalis michalis Agassiz 



32. Eye small, less than one-fourth length of head in adult; muzzle conical, the 

 head subtriangular in outline; dorsal fin with a black blotch on membranes 

 between the posterior rays, except in young; dorsal subquadrate in outline, 



the last rays in adults much more than half as long as the longest 



Spotfin Shiner, Notropis »pilopteru.s (Cope) 



Eye large, more than one-fourth length of head in adult; muzzle bluntly 

 rounded, the head not closely approaching a triangle in outline; dorsal fin 

 without a black blotch on the membranes between the posterior rays; dorsal 

 subtriangular in outline, the last rays less than half as long as the longest. 33 



33. A large, conspicuous, and well-defined black spot on the base of the caudal 



fin; size larger, commonly more than 3 inches in total length 



Northern Sixjttail Shiner, Notropis hudsonius hudsonlus (Clinton) 



No large, conspicuous, and well-defined black spot on the base of the caudal 

 fin, spot when developed not sharply set off from lateral band; size small, 

 maximum total length about 3 inches 34 



34. Lateral band blackish, sometimes very indistinct in life, continued forward 

 through eye and around muzzle; lateral line incomplete, except in Notropis 



anogemis ,35 



Lateral band dusky or obsolete, not definitely continued forward through 



. eye and around muzzle; lateral line complete 38 



35. Mouth extremely small, almost vertical; upper jaw extending only to below 

 anterior nostril; teeth of inner row lacking; lateral line nearly or quite com- 

 plete: peritoneum blackish Pugnose Shiner, Notropis anogenns Forbes 



Mouth rather large, moderately oblique; upj:)er jaw extending beyond 

 anterior nostril almost to below eye; teeth of inner row frequently developed; 

 lateral line incomplete; peritoneum silvery 36 



3G. Lateral band in surrounding muzzle confined to chin and premaxillaries; 

 mouth more oblique, making an angle of less than 60 degrees with the 

 vertical; teeth of outer row 1 or 2, usually developed; blackened borders to 



lateral-line pores not expanded into crescentic bars 37 



Lateral band in surrounding muzzle encroaching on snout above the pre- 

 maxillaries but not on the chin; chin not black; mouth less oblique, making 

 an angle of much more than 60 degrees with the vertical; teeth of outer row 

 lacking; dark borders to lateral-line ix)res expanded to form prominent 

 crescent-shaped black crossbars Northern Black- 

 nose Shiner, Notropis heterolepis heterolepis Eigenmann and Eigenmann 



37. Mouth more oblique, making an angle of decidedly less than 60 degrees 

 with the vertical; jaws equal or nearly so; snout sharp; scales of next row 

 above lateral line on trunk with dark bars alternating with the black marks 



on the lateral-line scales, producing a zigzag appearance; anal rays 8 



t Blackchin Shiner, Notropis heterodon (Cope) 



Mouth less oblique, making an angle of little less than 60 degi-ees with the 



