208 MR. C. TATE REGAN ON THE 
mouth. ‘These varieties scarcely seem worth recognition; in all young specimens the 
spots are large and the lower surface of head and abdomen 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, pl. v. fig. 1. 
Depth of body 63-64 times in the total length, length of head 54 times. Depth of 
head 14-2 times in its length, breadth of head 1} times, length of snout 1§ times, 
diameter of eye 7-8 times, interorbital width 24 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. 
Seutes spinulose (in males strongly spinate), the anterior and upper scutes carinate, 
32 in a longitudinal series, 10 between dorsal and adipose fin, 17 between anal and 
caudal. Supraoccipital entirely margined posteriorly bya single scute. Lower surface 
of head and abdomen, in the adult, almost completely covered with small granular 
<eales. D.17, the first ray nearly as long as the head, the last }-# as long; length 
of base of dorsal 14 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, Piecosromus Frest.£. (Plate 1X. 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 43 times. Depth of head 
twice in its length, breadth of head 1} times, length of snout 1} times, diameter of eye 
84 times, interorbital width 54 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 (?in 
males only), those of the upper series carinate, 55 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.1 7, the first ray 
nearly as long as the head, the last $ as long; length of base of dorsal 13 times in its 
distance from the adipose fin, A. 14. Pectoral spine extending to base of ventral, 
armed in its outer half with very long curved bristles (tin males only). Caudal slightly 
