414 CALIFORNIA ACADEMY OF SCIENCES. 



Posthumeral keel not extending posterior to the ven- 

 tral fins. Lateral plates not carinate. 



Last dorsal ray Ih in the first, which is much shorter 

 than the head. Base of the dorsal fin equal to its dis- 

 tance from the caudal fin. 



Pectoral fins extending little beyond origin of the ven- 

 tral s. 



Tip of snout with a small naked area. 



Region between the ventrals naked, except sometimes 

 a narrow median bar; in front of this the ventral region 

 is usually covered with granular plates, the granules on 

 the sides of the belly largest. 



Caudal very obliquely emarginate. 



Color markings indistinct in the specimens examined, 

 the spots on the caudal fin'sometimes forming vertical 

 bars. 



Sixteen specimens, .125-. 16 m. Rio Preto; Rio Puty. 



Types. 



LXXXIII. Rhinelepis. 



Rhinelepis Spix, Gen. et Spec. Pise. Bras. 4, pi. 2, 1829 

 (aspera). 



Type: Rhinelepis aspera Spix. 



The larger species of this genus resemble the broad, 

 flat-headed species of Plecostomus from which they dif- 

 fer in the absence of the adipose fin. R. carinatus re- 

 sembles more the species of Hisonotiis, Otocinclus and 

 Microlepidogaster . 



Habitat: Parahyba; Rio San Francisco; Rio Car- 

 andahy; Amazons from Manacapuru to Huallaga. 



ANALYSIS OF THE SPECIES OF RHINELEPIS. 



a. Ventral surface mostly naked. 



h. Lateral plates not keeled, head not crested. parahyhtB 369. 



bh. Lateral plates all keeled; occipital with three crests. 



lophophanes 370. 



