Jordan and Evermann. Fishes of North America. 213 



DIONDA (a coined name) : 

 aa. Teeth comparatively short, distinctly hooked ; suborbitals moderate ; plumbeous species, 



usually \vith dark lateral band, the adult less than 3 inches long. 

 d. Scales in lateral line 32 to 43. 



<>. Body rather slender, the depth 4 to 4% in length. 



/. Scales large, 32 to 34 in lateral line. SERENA, 343. 



ff. Scales smaller, usually 37 to 40 in the lateral line. 



g. Sides with a dark lateral band, ending in a more or less distinct dark spot 



at base of caudal. 



7t. Cleft of mouth about 5 in head ; snout bluntish. KPISCOPA, 344. 



hh. Cleft of mouth about 4 in head, the snout more acute. NUBILA, 345. 



gg. Sides without distinct dark lateral band or caudal spot ; body elliptical in 



outline ; eye 3% in head, rather longer than snout. AMARA, 346. 



ee. Body rather stout, the depth 3% to 3% in length ; scales about 37 ; sides with 



dusky band and caudal spot. MELANOPS, 347. 



II. Scales in lateral line 50 to 60 ; body rather slender, the depth 4% in length. 



PLUMBEA, 348. 



Subgenus HYBOGNATHUS. 

 840. HYBOGNATHUS NUCHALIS, Agassis. 



(SILVERY MINNOW.) 



Head 4| to 5 ; depth 4i ; eye 4. D. 8 ; A. 7. Teeth 4-4 ; scales 5-38-4. 

 Body elongate, comparatively slender. Head moderate, rather short, the 

 profile evenly curved ; suborbitals broad, the anterior about twice as long 

 as deep. Eye moderate, rather longer than muzzle. Upper jaw heavy ; 

 lower jaw thin. Scales large and silvery. Lateral line decurved ; 12 to 

 14 large scales in front of dorsal. Intestines very long, 7 to 10 times 

 length of body. Olivaceous green above, translucent in life; sides clear 

 silvery, with bright reflections ; fins unspotted, coloration becoming 

 dusky in specimens living in dark waters. Length 4 to 7 inches. A 

 graceful minnow, abundant in clear streams from the Delaware and Neuse 

 to the Upper Missouri and southward to Georgia and Texas ; common in 

 or near large rivers. Variable; tangible varieties are : subspecies placita, 

 (Girard),from the Arkansas and Missouri rivers, the eye smaller, 5 in 

 head; the snout depressed and blunt, with very small mouth; subspecies 

 reyia, (Girard), Potomac River, more than 6 inches long (western forms 

 are usually less), with deeper body and larger eye, 3f in head ; the form 

 called osmerinus, from Delaware River, is not evidently different from 

 nuchalis, which is the common form of the Missouri Valley, (nuchalis, 

 pertaining to the nape.) 



Hijbognathus nuchalis, AGASSIZ, Amer. Journ. Sci. Arts, 1855, 224, Quincy, Illinois. (Coll. Dr. 



Watson.) Ci'NTHER, Cat., vn, 184, 18G8 ; JORDAN & GILBERT, Synopsis, 156, 1883. 

 Hybogmdhns placilus, GIRARD, Proc. Ac. Nat. Sci. Phila., 1856, 182, sluices of the Arkansas 



River, Fort Makee, Arkansas. (Type, No. 87. Coll. Dr. Suckley.) 

 nylutgnatlau craiwi, GIRARD, Proc. Ac. Nat. Sci. Phila., 1856, 182, Fort Pierre, Nebraska. 



(Coll. Dr. Evans.) 

 Hijbngnatltm regius, GIRARD, Proc. Ac. Nat. Sci. Phila., 1856, 209, Potomac River. (Coll. 



Girard.) GI-NTHER, Cat., vn, 185, 1868. 

 Hylognathm osmerinus, COPE, Proc. Amer. Phil. Soc. Phila., 1870, 466, Raritan River, New 



Jersey. (Coll. C. C. Abbott.) 



