254 PATAGONIAN EXPEDITIONS : ZOOLOGY. 



g. Dorsal short ; lower jaw composed of three elements ; teeth minute, in a single 

 series ; gill-membranes grown to the isthmus ; lower jaw with a longitudinal 

 extent ; premaxillaiy rudimentary. VII. Chilodina;, American. 



gg. Dorsal elongate, with 17-23 rays; fourth gill arch with an accessory respiratory 

 organ ; lower jaw composed of two elements ; teeth minute, ciliform, in a single 

 series in each jaw ; anterior air bladder partly enclosed in a bony capsule. 



VIII. CitharinincB, African. 

 ana. Teeth well developed, fixed in the jaws ; an adipose fin or none. 



h. Maxillary not rudimentary, not ankylosed with the premaxillary ; premaxillaries not 

 coossified ; teeth compressed, truncate, notched, denticulate or serrate ; sometimes 

 canines also present. (See also Bramocharax.) Alimentary canal short. 

 i. Belly rounded before the ventrals ; teeth truncate, notched or serrate. 



j. No scales ; no adipose ; teeth in premaxillary in two rows, in maxillary and 

 mandible in single series, narrow at base, broad at tip, 3-5 pointed ; a long 

 fontanel in occiput. IX. GyninocharacinincB, south of Buenos Aires. 



jj. Body fully scaled. 



k. Skull with a parietal, and usually in the American genera, with a frontal 

 fontanel ; teeth in the lower jaw not in two complete series. 

 /. Premaxillary and mandible with a single series of teeth. 

 7n. Dorsal with 1 1 rays or fewer. 



71. Large frontal and parietal fontanels. Gill-membranes united, 

 usually joined to the isthmus, free from it in some genera ; 

 intestine short ; mouth small with little or no lateral ex- 

 tent ; nares close together or remote. 



X. AnostoinatincB, American. 



nn. No frontal fontanel, parietal fontanel if present confined to 



the occipital region. Gill-membranes sometimes slightly 



united, usually free from each other and from the isthmus ; 



nares remote ; mouth minute ; adipose present or absent ; 



no teeth on maxillary. XI. Nannosioniatince, American. 



nun. Gill-membranes free from the isthmus and from each 



other ; nares close together, separated by a flap only ; 



fontanels large, separating the parietals and the frontals to 



at least the middle of the eye ; adipose always present ; 



maxillary with teeth. XII. Aphiocharacina, American. 



111111. Dorsal with i 5 rays. XIII. CrenuchincB, Km&r\cdx\. 



11. Premaxillary with two or more series of teeth ; nares approximate. 



0. Gill-membranes united, free from isthmus ; a single series of teeth 



in the lower jaw. XIV. Igiianodcctince, American. 



00. Gill-membranes free from each other and from the isthmus. 



/. Opercle prolonged ; premaxillary with two, mandible with 

 a single series of teeth ; belly not keeled ; gill-membranes 

 free from isthmus ; rakers close together. 

 q. Adipose fin present ; no rakers on lower limb of an- 

 terior gill-arch; anal long (31); dorsal in part in 

 fro nt of anal. XV. Diapomince, Rio Grande do Sul. 



