280 FISHES. 



dorsal behind ventrals, nearer snout tlian caudal; uni- 

 form bluish gray; often with a dark shoulder blotch; D. 

 13; A. 32; lat. 1. 55. Cape Cod to Cape Hatteras, 

 chiefly marine, but often land-locked in ponds, where it 

 becomes D. irisociabile^ Abbott. 



Var. heierura, (Raf.) Jor. Ohio Gizzard Shad. 

 Thread Shad. Head 3^ in length; depth 2f to 3 in 

 length; dorsal about midway, slightly behind ventrals; 

 dorsal filament nearly oiie-fourth length of body; bluish, 

 sides bright silvery. Ohio R. and lower Mississippi, 

 apparently not descending to the Sea; also escaped into 

 the Great Lakes. The difference between the curve of 

 the ventral and dorsal outlines is greater in heterura 

 than in the Eastern variety. 



SUB-ORDER.-EYEIsrTOG]SrATHL 



(The Garp-Uke Fishes.) 



FAMILY CVIIL— CYPRINID^. 



{The Minnoios.) 

 Head naked, body scaly (excejDt in Meda^ etc.); mar- 

 gin of upper jaw formed by intermaxillaries alone; 

 mouth toothless; lips much less developed than in the 

 C atostomoids ^ barbels two to four (absent in most of our 

 genera and not large in any); lower pharyngeal bones 

 well developed, falciform, nearly parallel with the gill 

 arches, each provided with one to three series of teeth 

 in small number, rarely more than seven on each side; 

 belly usually rounded, rarely compressed, never serrated; 

 gill openings moderate, separated by a narrow isthmus; 

 no adipose fin; dorsal fin (in all our species) short, with 

 less than ten rays; air bladder usually large, commonly 

 divided into an anterior and a posterior lobe, rarely 



