176 CALIFORNIA ACADEMY OF SCIENCES. 



As already stated Arius albicans is a distinct species. 



We add here descriptions of the more striking varie- 

 ties represented in the museum. We have not made 

 any reference to the teeth, as they are such a variable 

 quantity in all the varieties. The variety with plicate 

 lips (maculatus ?) seems to be more frequently destitute 

 of teeth on the vomer than the others. Intermediate 

 forms between all of these varieties are in the collection. 



124a. Lips distinctly plicate; maxillary barbel ex- 

 tending to base of anal, or slightly longer; mental bar- 

 bels about to base of pectoral fin; postmental past mid- 

 dle of pectoral; mentals and postmentals compressed. 



Eye 2J-2f in snout, 5-5 J in length of head, IJ-lf in 

 interorbital. 



Width of mouth about 3 in head; the teeth of the 

 upper jaw scarcely projecting beyond the lower; depth 

 of the intermaxillary band of teeth 4J-4^ in its width. 



Distance between anterior and posterior nasal open- 

 ings about equal to the eye. 



Opercle scarcely longer than the diameter of the eye. 



Pectoral plate elongate, subelliptical, its width about 

 3 in its length. 



Caudal lobes pointed, the upper longer than the head. 



Adipose dorsal 4 4J in the length. 



Dorsal spine about equal to the head in length; pec- 

 toral spine 1|-1J. Ventral fin 1J-2 in head. 



Body with four or five rows of large brown spots; spots 

 on head; sometimes the spots are much smaller and 

 irregularly scattered. 



"Lacepede described his Pimelodus maculatus after 

 Commerson who had specimens from the Rio Plata." 

 (Val.) The specimens in the museum agree closely with 

 the description given by Valenciennes and the figure 

 by Liitken in Velhas Flodens Fiske, page 165; they 

 are from the Rio das Velhas; Uraguay; Giquitiba; Rio 

 Grande and Buenos Ayres. 



