252 Field Museum of Natural History — ZoOlogy, Vol. X. 



which vary in size, shape and number among individuals; fins all brown- 

 ish green with pale green spots. 



The Panama collection contains 56 specimens, ranging from 45 to 

 255 mm. in length. Fifty-four of these are from the Rio Chagres Basin. 

 The other two were taken in the Rio Chorrera, a small stream on the 

 Pacific slope west of Panama City. 



Habitat: Rio Chagres and Rio Chorrera, Panama. 



9. Ancistrus spinosus sp. nov. 



Type No. 8942, F. M. N. H.; length 135 mm.; Rio Calobre, 

 tributary of the Rio Bayano, Panama, 



Head 2.65 to 2.77; depth 4.6 to 4.7; D. I, 7; A. I, 4; lateral scutes 24. 



Body broad anteriorly; caudal peduncle posteriorly compressed; 

 head broad; interorbital width nearly equal to the depth of body, 1.95 

 in head; snout obtuse, the naked portion narrow in the female and with 

 only 4 small tentacles, much wider in the male with a fringe of tentacles 

 along the margin and a V-shaped patch on the upper surface at the tip; 

 length of snout 1.63 to 1.7 in head; eye 8.75; mouth wide; the lips 

 expanded; the lower lip with a small barbel, shorter than eye, on its 

 lateral margin; the premaxillaries and dentaries equal in length; man- 

 dibular ramus 3.1 to 3.6 in interorbital width; teeth slender, bifid, 

 curved inward near the tips; interopercle with from 8 to 12 spines, 

 curved outward and forward near the apices, longer in the male than 

 in the female; sculpture of head without ridges or carinations; scutes on 

 back and sides not carinate, their margins very strongly serrate, espe- 

 cially in the male; occipital posteriorly bordered by 3 scutes; the second 

 median scute with an evident median suture; 6 scutes between dorsal 

 and adipose ; 11 or 1 2 between anal and base of caudal ; lower surface of 

 head and abdomen naked; dorsal fin very high, the posterior rays when 

 deflexed reaching past origin of adipose, the spine 1.15 to 1.2 in head; 

 base of dorsal equal to distance from the base of its last ray to base of 

 caudal; adipose fin well developed; caudal fin with a nearly straight 

 oblique margin, the lower rays the longest; anal fin small, its origin 

 sHghtly behind vertical from base of last ray of dorsal; ventral fins 

 reaching well beyond base of anal; pectoral fins very long, reaching to 

 or past the middle of ventral, the spine a little longer than the head. 



Color uniform dark above. The male plain brownish below; the 

 female with faint pale spots on abdomen; fins in male plain brownish, 

 in female with faint pale spots. 



Apparently a rare species. There are at hand only 2 specimens, a 

 male and female, respectively 130 and 135 mm. in length. The male 

 was taken at the mouth of the Rio Yape, tributary of the Rio Tuyra; 



