286 Field Museum of Natural History — Zoology, Vol. VII. 



form teeth; premaxillary not protractile; no adipose fin; caudal fin 

 forked ; gill membranes free from the isthmus ; gill rakers few, short ; 

 stomach horseshoe-shaped, without blind sac; pyloric coeca i; air 

 bladder large, with open duct; no oviducts, the eggs falhng into the 

 body cavity before extrusion. 



Genus Hiod(»ii Le Sueur. 



Body much compressed, the ventral surface reduced to a narrow 

 edge or keel; belly not serrated; head without scales; mouth ter- 

 minal, rather large, oblique, and armed with sharp teeth; premax- 

 illary not protractile. 



a. Belly in front of ventrals with a sharp edge over which the scales 

 do not pass; dorsal fin with 9 developed rays, alosoides, 286 

 aa. Belly in front o'f ventrals without sharp edge, the scales pass- 

 ing over it ; dorsal fin with 11 or 12 developed rays. 



tergisus, 286 



liiodon alosoides (Rafinesque). Northern Mooneye. 



Head 4.5 to 4.9; depth 3.3 to 3.7; D. 9; A. 31; scales 56 to 58. 



Body elongate, much compressed; head rather small; mouth 

 large, the jaws armed with sharp teeth; interorbital space 3.6 to 4.0 

 in head; diameter of eye 3.6 to 4.0; snout 4.9 to 5.9; dorsal fin in- 

 serted behind front of anal; lateral line complete. 



Color bluish above; sides and belly silvery, with more or less 

 golden lustre anteriorly and bluish and pinkish posteriorly. 



Length about 12 inches. 



This species ranges from the Saskatchewan through the Great Lake 

 Region to Ohio, being most abundant in the northern part of its 

 range. 



Hiodon tergisus Le Sueur. Toothed Herring; Mooneye. 



Head 4.0 to 4.4; depth 3.0 to 3.3 ; D. 11 or 12; A. 28; scales 55. 



Body much compressed, mouth smaller than in preceding species, 

 the jaws armed with pointed teeth, interorbital space' 3.9 to 4.0 in 

 head; diameter of eye 2.8 to 3.6; snout 4.0 to 5.5; maxillary not 

 reaching past middle of orbit, its length 2.1 to 2.5 in head; dorsal fin 

 inserted in front of anal ; lateral line complete. 



Color pale olive-buff above, with faint steel-blue lustre; sides 

 silvery, lighter below. 



Length 10 or 12 inches. 



The range of this fish is much the same as the preceding. 



