SOUTH AMERICAN NEMATOGNATHI. 251 



ANALYSIS OF THE SPECIES OF HEMIDORAS. 



a. Lateral scutes well developed from the dorsal plate backward. 

 b. Fontanel not continued as a groove to tip of occipital process. 

 c. Snout short, rounded. 



d. Vertical diameter of eye little less than the longitudinal diame- 

 ter. 

 e. Upper jaw without teeth. 



f. Dorsal spine shorter than the pectoral spine, not reaching 

 origin of adipose fin. Adipose shorter than anal fin; pectoral 

 pore large. Snout (except the area between the anterior and 

 posterior nares), preorbitals and preopercle, granular. 



natlereri 189. 



ff. Dorsal spine as high as the pectoral spine. Snout, to the 

 posterior nostrils and cheeks, covered with skin. Humeral 

 process reaching to the first lateral plate. Adipose fin about 

 as long as the anal fin. Pectoral pore wanting. D. I, 6; P. 

 I, 7; V. 7; A. 13-14; Lat. 1. 29-30. (Kner.) brevis 190. 



ee. Teeth in both jaws; snout and cheeks naked. Humeral pro- 

 cess ending in front of the first lateral plate. 



g. Caudal peduncle with a single large plate on its upper and 

 lower surfaces; coracoid process turned up, meeting the first 

 lateral scute. Maxillary barbels not reaching beyond base 

 of pectorals. Pectoral spine as long as the dorsal spine, 

 reaching beyond base of ventral fins. Brown, with blackish 

 spots and points. D. I, 6; P. I, 8; V. 7; A. 11; Lat. 1.29-30. 

 (Kner.) fimbriatus 191. 



gg. Caudal peduncle naked above and below; coracoid process 



straight; first lateral plates not enlarged. Dorsal spine shorter 



than the pectoral- spine which does not reach the base of the 



ventrals. Maxillary barbels not reaching to the gill-opening. 



Sides and back brownish, with darker spots. D. I, 6; P. I, 



7; V. 7; A. 13; Lat. 1. 29-30. (Kner.) punctatus 192. 



dd. Vertical diameter of the orbit half the longitudinal diameter; 



dorsal spine longer than the pectoral spine; both spines serrate 



on both margins. Snout pointed, compressed, strongly decurved 



in front of the eyes; longitudinal diameter of the eye 2 in the 



head; its vertical diameter 2 in the snout, 1 in the interocular, 



5-J in the head. Snout, interorbital, cheeks and most of the head 



naked. Fontanel almost as wide as the interorbital, extending 



behind the eyes; anterior nares nearer to the eye than to the 



snout. No teeth on the intermaxillaries. Maxillary barbels 



reaching to the gill-opening. Humeral process twice as long as 



high. Lateral plates small, largest on the caudal peduncle, which 



does not bear shields on its upper and lower surfaces. Brownish, 



ventral surface whitish. Depth 5; D. I, 6; P. I, 9; V. I, 6; A. 12; 



Lat. 1. 37-38. (Kner.) lipophthalmus 193. 



