502 PROCEEDINGS OF THE ACADEMY OF [July, 



23. Hypoptopomus thoracatum Giinther. 



One specimen (No. 126). 80 mm. Matto Grosso. Collected b}^ 

 Dr. CarlTernetz. 



24. Plecostomus commersoni (Val.). 



Two specimens (No. 113). 170 and 220 mm. Matto Grosso. Col- 

 lected by Dr. Carl Ternetz. 



25. Plecostomus vermicularis Eigenm. and Eigenm. 



One specimen (No. 213). 70 mm. Arroyo Trementina. Caught 

 in a fish trap. 



26. Plecostomus boulengeri sp. nov. 



Type No. 9,868, one specimen (No. 112). 10 cm. Co-type No. 

 9,869, one specimen (No. 112). 6 cm. Both specimens from Matto 

 Grosso or Asuncion. Collected by Dr. Carl Ternetz. 



Head j^ointed; a low ridge from between the nares to the snout; 

 three distinct ridges on the back part of the head. Occipital process 

 short, triangular, bordered by a single nuchal plate. The nuchal 

 plates bicarinate. Only the upper lateral plates on the anterior part 

 of the body keeled. The humeral ridges moderate, extending over 

 the first 4-5 plates. Tip of the snout naked. Belly covered with 

 small granular plates, except for a small area in front of each ventral. 

 In the younger specimen the belly is entirely naked. 



Eye 2-2^ in interorbital, 2^-3 in snout, 4-4^ in head. Eye larger 

 in the younger specimen, 2^ in snout, 4^-4f in the head. 2 in the inter- 

 orbital. 



Base of dorsal fin ecjuals distance from dorsal to posterior end of 

 adipose dorsal. First dorsal ray H in the distance from dorsal to tip 

 of snout, slightly longer than head. Last dorsal ray H-lf in first 

 dorsal ray. 



Caudal obliquely truncate; outer rays not produced. 



Head and body covered with small round spots ; those on the head 

 minute; those on the belly large, leaving a mere reticulation of the 

 lighter ground color. The fins reddish, the dorsal with four rows of 

 large round spots ; in each row a single spot on each interradial mem- 

 brane. In the larger specimen the two upper rows are indistinct; in 

 the younger specimen all the dorsal spots are indistinct. Caudal with 

 four oblique bands. The pectorals and ventrals each with four dark 

 bands. Anal dusky with a single band. 



Lat. plates 26; head 4^; depth 5; D. I, 7; \. 5; A. 5; P. I, 6. 



This species is evidently related to commersoni, scahriceps and p/c- 

 costomus. It agrees with the latter in the numlier of lateral scutes. 



