Description of Neiv Nematognathoid Fishes from Brazil 9 



Those genera of Plecostominae. destitute of an ''adispose" dor- 

 sal fin, may be distinguished by the following key : 



(#.) Temporal plate perforate. (Species of small size.) 

 (b.) Ventral surface covered by three series of large plates; 

 dorsal fin inserted over the origin of the ventrals. 



Oclocinclus. 

 (bb.) Ventral surface covered by minute granular plates; 

 dorsal fin inserted far posterior to the ventrals, its origin equi- 

 distant from tip of snout and base of caudal. 



Microlepidog aster, 

 (aa.) Temporal plate imperforate. 



(c.) Ventral surface covered by about three series of large 

 plates. (Species of small size.) Hisonotus. (* 



(cc.) Ventral surface naked or covered by minute granular 

 plates. (Usually species of large size.) 



(d. ) Margin of the snout granular. Rhinelepis. 



(dd.) Margin of the snout with spines; lateral . plates isolate. 



Acanthicus. 

 Microlepidog aster perforatus sp. nov. 



Type: No. 8,182; one specimen. .032 m. to base of caudal. 

 Rio Carandahy, Brazil. 



Broad and depressed anteriorly, the depth less than the width. 

 Head broad, depressed, its depth little more than two in its 

 length to the end of temporal plate ; its width iy£ in its length. 

 Snout narrow, pointed ; loreal region concave. Eye 4 in snout, 

 8}4 in head; interorbital concave, equal to the post-orbital por- 

 tion of the head. 



All of the plates hispid, most so on the tail, not keeled. Belly 

 entirely covered with small granular plates to between the ven- 

 trals. Lat 1. 27. 



Rhinelepis lophophanes sp. nov. 



Type: No. 8,164; one specimen .018 m. to base of caudal. 

 Santa Cruz, Brazil. Collected by Dom Pedro II. 



Greatest depth equal to the greatest width. Occipital with 

 three strong spiniferous ridges, a short median one and two 

 longer lateral ones ; similar crests extending from posterior mar- 

 gin of orbit to edge of temporal plate. Nasal pits margined by 

 spiniferous ridges. Lower surface of head naked, margined by 

 a series of recurved spines. Coracoid and scapula granular; 

 belly with a small granular plate between posterior margins of 

 ventrals; a larger plate behind the pectoral. Lateral and dorsal 

 plates keeled. D. I, 7; A. 6; Lat. 1. 22. 



This species differs widely from the other species of Rhinelepis, 

 as may be seen from the following comparison : 



a. Ventral surface mostly naked. 



•J Gen. Nov. in press. 



