242 SILURID^. 



/3. Dorsal fin eight-rayed. 

 * Scutes of the body with distinct keels. 



3. Chsetostomus medians. 



? Ancistrus medians, Kner, Hypostom. p. 256. 



D. 1/7. A. 5. P. 1/6. L. lat. 24. 

 Head large, not depressed, broader than long, its length being 

 contained thrice and a third in the total (without caudal) ; snout 

 very broad, roiinded in front. Orbit elevated, iuterorbital space rather 

 concave ; eye large, its distance from the posterior end of the head 

 being equal to its diameter, which is more than one-half of the width 

 of the interorbital space. The margin of the snout is roughly granu- 

 lated ; interoperculura with a bundle of about thirtj'-five setiform 

 spines, the longest of which are one-thii'd of the length of the head, 

 and extend backwards to behind the root of the pectoral. Thorax 

 and beUy neaiiy entirely naked, being covered with patches of small 

 granulations only laterally and anteriorly. Dorsal fin nearly as high 

 as long, the length of its anterior rays being rather less than that 

 of the head ; the length of its base is nearly equal to its distance 

 from the caudal ; there are six scutes between the two dorsal fins. 

 Caudal fin obliquely truncated, the loAver lobe being much longer 

 than the upper. The pectoral spine is strong, extending to the 

 middle of the ventral fin, and covered behind with setiform spines; 

 the ventral fins extend somewhat behind the anal. Thirteen scutes 

 between anal and caudal ; scutes of the body with a prominent ser- 

 • rated keel and with radiating rough striae ; posthumeral ridge rather 

 distinct. Brown, all parts covered ^vith round black spots of moderate 

 size ; those on the head are smaller, and those on the beUy less nu- 

 merous, than those on the back. The spots on the dorsal fin form two 

 series on each interradial space, partly covering the rays. 



Surinam. 

 a-b. Fine specimens. Purchased of Mr. Kappler. 



I have no doubt that our specimens are identical with Ancistrus 

 medians of Kner, although he describes the beUy as densely covered 

 with small shields ; M. Kner saw his specimens in the Stuttgart 

 Collection, which received them from the same source as the British 

 Museum. 



4. Clisetostomus pictus. 



Ancistrus pictus, Kner, Hypostom. p. 277. taf. 4. fig. 2. 

 D. 1/7. A. 6. L. lat. 23-24. 

 Head broad, much depressed, without prominence on the occiput ; 

 its length is one-third of the total (without caudal). Eye of mode- 

 rate size, two-thirds of the width of the interorbital space ; an obtuse 

 ridge runs from the orbit to below the nostril. Margin of the snout 

 granulated, except in the middle of its extremity. Interoperculum 

 with a bundle of about twenty setiform spines, the longest of which 

 are one-third as long as the head. Scutes of the sides of the body 

 keeled. Dorsal fin rather longer than high ; the pectoral spine ex- 



