208 ME. C. TATE BEGAN ON THE 



mouth. These varieties scarcely seem worth recognition ; in all young specimens the 

 spots are large and the lower surface of head and ahdomen partially naked, and the 

 persistence of these features in the adult must be regarded as cases of individual 

 variation only. 



4. Plecostomus spinosissimus. 



Plecostomus spinosissimus Steind. Denkschr. Ak. Wien, xlii. 1880, p. 98, pi. v. fig. 1. 



Depth of body 6|-6f times in the total length, length of head 3f times. Depth of 

 head If- 2 times in its length, breadth of head ljj times, length of snout If times, 

 diameter of eye 7-8 times, interorbital width 2f times. Length of mandibular ramus 

 3 times in the interorbital width. Snout narrowed anteriorly ; supraorbital margins 

 raised ; supraoccipital with median ridge ; temporal plates not distinctly carinate. 

 Scutes spinulose (in males strongly spinate), the anterior and upper scutes carinate, 

 32 in a longitudinal series, 10 between dorsal and adipose tin, 17 between anal and 

 caudal. Supraoccipital entirely margined posteriorly by a single scute. Lower surface 

 of head and abdomen, in the adult, almost completely covered with small granular 

 scales. D. I 7, the first ray nearly as long as the head, the last J-f as long ; length 

 of base of dorsal lj times in its distance from the adipose fin. A. I 4. Pectoral 

 spine extending to base of ventral (in males armed with long curved bristles in its 

 outer half). Caudal slightly emarginate. Caudal peduncle 7 times as long as deep. 

 Numerous dark spots on head, body, and fins. 



Total length 250 mm. 



Two specimens : Guayaquil, W. Ecuador. 



5. Plecostomus fest.e. (Plate IX. fig. 1.) 



Plecostomus festa Bouleng. Boll. Mus. Torin. xiii. 1898, no. 329, p. 11. 



Depth of body 8 times in the total length, length of head 4-| times. Depth of head 

 twice in its length, breadth of head 1^ times, length of snout If times, diameter of eye 

 8J times, interorbital width 3^ times. Length of mandible 2| times in the interorbital 

 width. Snout narrowed anteriorly ; supraorbital margins raised ; supraoccipital with 

 median ridge ; temporal plates not distinctly carinate. Scutes strongly spinate (lin 

 males only), those of the upper series carinate, 33 or 34 in a longitudinal series, 

 11 between dorsal and adipose fin, 19 between anal and caudal. Supraoccipital entirely 

 margined posteriorly by a single scute. Lower surface of head and abdomen, in the 

 adult, almost completely covered with small granular scales. D. I 7, the first ray 

 nearly as long as the head, the last f as long; length of base of dorsal 1§ times in its 

 distance from the adipose fin. A. I 4. Pectoral spine extending to base of ventral, 

 armed in its outer half with very long curved bristles (1 in males only). Caudal slightly 



