250 CALIFORNIA ACADEMY OF SCIENCES. 



188, Oxydoras amazonum, 



Hhinodoras amazonum Steindachiier, SB. Ak. VVien, Ixxi, 141, pi. 



ii, 1875 (Amazon near Teffe). 

 Oxydoras amazonum Eigenm. & Eigenm. Proc. Gal. Acad. 2d Ser. 



i, 159, 1888. 

 Habitat: Teffe. 



XLII. HEMIDORAS. 



Doras Lacepede, Hist. Nat. Poiss. v, 116/1803 (cari- 

 natus and costatus). 



Doras Bleeker, Nederl. Tijdschr. Dierkuiide, i, 13, 

 1863 (carinatus ; not Doras Ouv. & Val.) 



Oxydoras Kner, SB. Ak. Wien, xvii, 1855. (sp.) 



Hemidoras Bleeker, Ichthyol. Arch. Indici. Siluri, 1858 

 (stenopeltis). 



Hassar Eigenm. & Eigenm. Proc. Cal. Acad. 2d Ser. i, 



158, 1888. 



Type: Doras stenopeltis Kner. 



The genera Hemidoras, Oxydoras, and Doras, as under- 

 stood in this paper, correspond to and are respectively 

 coextensive with the genera Oxydoras, Rhinodoras, and 

 Doras of Dr. Gunther. 



Maxillary barbels and sometimes the mental barbels 

 with a series of short tentacles; mental barbels and 

 sometimes all the barbels connected by a broad mem- 

 brane. Snout usually naked. Sides with a series of 

 hook-bearing plates. 



Habitat: Paranahyba ; Amazon and its tributaries; 

 Guiana. 



The deeper forms of this genus resemble very closely 

 the species of the genus Centromochlus, and those other 

 genera in which the dorsal plate has a descending pro- 

 cess behind. These forms usually have a movable sub- 

 dermal bone or cartilage descending from the dorsal 

 plate, which is represented in the mailed forms by the 

 first lateral plate. 



