256 PATAGONIAN EXPEDITIONS: ZOOLOGY. 



y. Belly compressed ; body long and narrow, knife-like anal long ; teeth unequal ; 

 a pair of large canines in the lower jaw in front, received in two grooves in 

 the palate ; palate with minute teeth ; gill-rakers reduced to slight denticles. 



XXVIII. CynodontiucB, American. 

 yy. Belly rounded or the body not long and narrow. 



z. No teeth on the palate ; snout comparatively short ; teeth all moderate in 

 size, sometimes strong canines ; gill-rakers strong ; nares approximate ; 

 gill-membranes free from isthmus. XXIX. CIuxracincE, American. 



zz. Teeth on the palatines. 



A. Snout very elongate ; palatine teeth minute, granular ; anal short ; 

 intestine short. XXX. Hydrocyniuie, American. 



AA. Snout moderate ; some of the teeth canines ; palatine teeth 

 conical, in a single series ; anal long ; intestine short. 



XXXI. AcestrovhamphincB, American. 

 X. No fontanel. 



B. An adipose fin. Premaxillarj' with a backward projecting process between the 

 maxillary and the palatines, the process provided with small teeth ; no occipi- 

 tal crest ; skull as in Erythrinina:. Snout much prolonged. 



XXXII. SarcodacitKB, African. 

 BB. No adipose dorsal ; skull above more or less truncate behind, the supraoccip- 

 ital confined to the posterior surface and carinated by a rudimentary or obso- 

 lete vertical crest ; adipose fin none ; gill-opening wide, the membranes slightly 

 united, free from the isthmus. Dorsal in advance of the anal, usually over or 

 a little behind the ventrals ; A. 10-13. 



c. Gape very wide, premaxillary and dentaries with strong canines ; lateral 



line developed ; caudal rounded. XXXIII. Eyythrinina. 



cc. Gape oblique ; maxillary with a few slender teeth, no canines ; lateral line 



obsolete or developed anteriorly only ; caudal forked or emarginate. 



Walls of the air bladder normal ; teeth all conical. 



• XXXIV. Pyrrhulinina, American. 



Genera of Tetragonopterin.e. 



a. Jaws equal, the lower not included ; mandibulaiy teeth meeting the second of the premaxillary 

 series. Premaxillary with two series of teeth. 

 b. Mandibles without conical teeth in front. 



c. Gill-rakers short, lanceolate ; anal long (29) ; lateral line complete ; maxillary with 

 conical teeth along half of its length ; premaxillaiy and mandibular teeth as in 

 Tetragonoptcrus. Scissor Giinther. 



cc. Gill-rakers setiform. 



d. Maxillary short, the snout and maxillary together less than half length of head. 

 Teeth of the lower jaw all alike in character and regularly graduated from in 

 front to the last tooth on the sides ; two teeth in the front row of the pre- 

 maxillary on each side ; teeth of the second row multicuspid incisors with 

 contracted base, their anterior and posterior surfaces alike, convex, without 

 distinct ridges. Lateral line complete. Dcxitcrodon Eigenmann. 



