iiioBoxrxi)-!;. 375 



Fam. 19. HYODONTID/E. 



Body covered with cycloid scales ; head naked ; 

 barbels none. Margin ol' the upper jaw formed by 

 the inleraiaxillaries mesially, and by the maxillaries 

 laterally, the latter being articulated to the end of 

 the former. Opercular apparatus complete. Adipose 

 fin none ; the dorsal fin belongs to the caudal portion 

 of the vertebral column. Stomach horseshoe-shaped, 

 without blind sac ; intestine short ; one pyloric ap- 

 pendage. PseudobranchiiE none ; air-bladder simple *. 

 Gill-openings wide. The ova fall into the abdominal 

 cavity before exclusion. 



Fresh waters of Xorth .Imerica. 

 Only one genus is known. 



1. HYODON. 



Iliodou, Lcanenr, Jvurn. Ac. Nat. Sc. Phi/ad. i. p. 'M>1. 

 Glossodon, Hccliel, in Husscffyer s lieisen, i. p. 1033. 



Body oblong, compressed, with a part of the abdomen trenchant ; 

 cleft of the mouth of moderate widtli, obliijuc, uj^per jaw overlap- 

 ping the lower. Eands of small teeth in the jaAvs, on the palatine 

 and pterygoid bones, along the vomei-, sphenoid, and hj'oid ; tongue 

 with an outer series of larger teeth. Dorsal tin short, opposite to 

 the anterior part of the anal, which is long ; caudal forked. Pectoral 

 and ventral fins well developed. Gill-membranes entirely sciiarate, 

 terminating in front below a transverse fold across the middle of 

 the throat, liranehiostegals in moderate iiumber. 



Eresh waters of 2(orth America. 



1. Hyodon tergisus. 



Tlie Moon-eye. 



Iliodou tergisus, Lesncur, I. c. p. 3GG; Kirthincl, liep. Zool. Ohio, 



pp. 170, li)5; and Bost. Joiirn. Nat. Hist. v. ]t>4(.), p. 338; Uckai/, 



New York Faun. Fish. p. 2Go, pi. 41. tig. 130; Cm: ^' Val. .\ix. 



p. 300, pi. 572 ; Girard, U. S. ^- Pac. R. R. Expcd. Fish. p. 332, 



pi. 75, figs, 1-4 (not 4-7). 



* Lo.siicur describes two addiiional small subglobiilar air-vessels at tlie auli- 

 rior ciitl ol" llic air-bladder, probably mistaking portions of llie someuhat lliii-Ui i 

 oulcv iiiembratic of llie air-l)latUler as se)wrule divisions. 



