35. HYODONTIDiE HYODON. 259 



Family XXXV.— IIYODONTID^. 



( The Moon Eyes ) 



Body oblong, compressed, covered with moderate-sized, brilliantly 

 silvery, cycloid scales. Head naked, short, the snout blunt. Mouth 

 moderate, oblique, terminal, the jaws about equal. Premaxillaries not 

 protractile. Maxillary small, slender, without evident supplemental 

 bone, articulated to the end of the premaxillary, and forming the lat- 

 eral margin of the upper jaw. Dentition \&rj complete. Premax- 

 illary and dentary bones with small, Avide-set, cardiform teeth. Max- 

 illaries with feeble teeth. A row of strong teeth around the margin 

 of the tongue, the anterior canine and very strong ; between these is a 

 band of short, close-set teeth. Vomer with a long, double series of close- 

 set, small teeth. Sinnlar series on the palatines, sphenoid, and ptery- 

 goids. Sides of lower jaw fitting within the upper, so that the denta- 

 rics shut against the palatines. Eye very large, the adipose eyelid not 

 much developed. Preorbitals very narrow. Nostrils large, those of 

 each side close together, separated by a flap. Gill-membranes not con- 

 nected, free from the isthmus, a fold of skin covering their base. jS^o 

 gular plate. Branchiostegals 8-10. Gill-rakers few, short and thick. 

 PseudobranchiaB obsolete. Lateral line distinct, straight. Belly not 

 serrated. Dorsal fin rather posterior. Anal elongate, low. Ventrals 

 well developed. Caudal strongly forked. No adipose fin. Stomach 

 horseshoe-shaped, without blind sac; one pyloric ccecum. Air-bladder 

 large. No oviducts, the eggs falling into the cavity of the abdomen 

 before exclusion. A single genus, with 3 known species, inhabiting 

 the fresh waters of North America. 



{UiiodontidcB Giiuthcr, vii, 375, 370.) 



1 E y.— Il¥ODOM Lo Sueur. 



Moon Eyes. 



{niodon Le Sueur, Jonrn. Acad. Nat. Sci. Pliila. i, 3G4, 1818: tyiie Hiodon terg'mis Le 

 Sueur.) 



Generic characters included above. {vosiSrj:;, hyoid; (hWv, tooth; 



"hyoid" is the bone shaped like the letter r, forming the base of the 



tongue.) 



* Belly in front of ventrals strongly carinatcd ; dorsal rays (dovolopcd) 9. 

 432. II. alosoidcs (Raf.) J. & G. 



Body closely compressed, becoming deep in the adult. Eye mod- 

 erate, smaller than in other species, about 3i in head, the maxillary 



