SOUTH AMERICAN NEMATOGNATHI. 47 



XXII. Ancistrus Kner. 



116. Ancistrus chagresi sp. nov.* 



Types, No, 8u26; two specimens (j^ & 9 •1-1--19 ^- Rio Chagres. Dr. 

 Maak. 



*As all the species of this genus are very much alike the followiog key will 

 serve to describe the new forms. 



a. Margin of the snout naked, provided with tentacles. The females with 

 a narrow naked margin and a single series of simple tentacles, or without 

 tentacles in calamila; males with a much broader naked area, a series of 

 simple marginal tentacles and a Y-shaped series on the middle of the 

 snout. 



h. Lower caudal lobe not produced, scarcely if any longer than the upper; 

 margin of caudal obliquely truncate, a dusky spot at the base of the first 

 dorsal membrane. D. I, 7; A. 4 or 5; lat. 1. 2i. 



c. Eye G-7% in the head; preopercular spines 11-15; median tentacles 

 of the male profusely branched; a small granular patch on the breast 

 below the base of the pectoral. chagresi 1. 



cc. Eye 7-10 in the head; preopercular spines 25 or more; median ten- 

 tacles of the male flattened, mostly simple; breast entirely' naked; 

 head broad, depressed; dark brown, thickly' covered with light spots 

 which are smallest and most regular on the hccid; ventral surface 

 lighter; fins dark brown irregularly spotted with light. stig))iaticus 2. 

 bb. Lower caudal lobe produced, much longer than the upper; margin of 

 the caudal sub-truncate. 

 d. Head longer thau broad. 



e. D. I, 7; dark brown, ventral surface lighter, everywhere with 

 small lighter spots very closely crowded and scarcely evident on 

 the dorsal surface; fins dusky, obscurely marbled; lat. 1. 23; 

 head 3. hoplogenys 3. 



ee. D. I, 8 or 9, rarely I, 7, Dark brown, sometimes everywhere 

 with dark spots which occasionally have a white center; fins 

 dusky, the base of the dorsal obscurely spotted like the body. 



temminkii 4. 



dd. Head as broad as long. calamita 5. 



hhh. Lower and upper caudal rays produced, the margin concave; 9-12 



interopercular spines. D. I, 7, rarely I, 8 in cirrhosus; a dark spot on 



base of first dorsal membrane. 



/. Dark brown, everywhere with rather large, light spots; dorsal 

 dark brown with wavy, interrupted horizontal bands; other fins 

 spotted with lighter. Head 2%-3. cirrhosus 6. 



ff. Dark brown, back with two darker cross-bands; head irregu- 

 larly marbled. cirrhosus dubius 6a. 

 f/f. Light or dark brown, everywhere covered with white dots 

 which are largest on the belly; fins colored like the body. 



Uucostictus 7. 



