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Show 1890.] SPECIES OF THE SILUROID GENUS ARGES. 451 A. longifilis, sabalo, taczanowskii, and peruanus inhabit the Andes of Peru, A. prenadilla and whymperi the Andes of Ecuador. I had originally confounded the two latter species, when Mr. Whymper submitted to m e his specimens for identification some years since, but a renewed examination has convinced m e that there are at least three kinds of " Preiiadillas " in Ecuador, instead of one as believed by Putnam. ARGES TACZANOWSKIT, sp. n. (Plate XLI. fig. 1.) Arges sabalo, part., Steindachn. Sitzungsb. Ak. Wien, lxxii. 1876, p. 598. D. 1/6. A. 1/6. P. 1/11. V. 1/4. Head as broad as long, one fourth of the total length (without caudal). Eyes very small, about one third the width of the interocular space, midway between the anterior nostril and the posterior border of the head, much nearer the upper extremity of the gill-cleft than to the posterior nostril; nostrils much nearer the end of the snout than to the eyes. Three rows of teeth in the prsemaxillary, mostly unicuspid, the outer row comprising about twenty teeth; mandibular teeth of the outer row larger and deeply notched. Labial lobes large and graulate all over; the cleft of the mouth measures one half the width of the buccal disk ; barbels measuring half the length of the head. Adipose fin one third of the total length (without caudal), very low and extending to the caudal. The origin of the first dorsal is one third nearer the end of the snout than the base of the caudal; the first ray is somewhat prolonged and its length equals the distance from the posterior nostril to the posterior extremity of the head. First pectoral ray prolonged, as long as the head, extending as far as halfway between the head and the anal, but not so far as the extremity of the ventrals. The latter fins originate slightly in advance of the dorsal, and measure exactly one half the distance between the base of their first ray (which is much thickened but scarcely prolonged) and the anal. Anal opening a little nearer the extremity of the ventrals than the origin of the anal. First anal ray three fourths the length of the ventral, halfway between the extremity of the pectoral and the caudal. The caudal fin is injured in the unique specimen examined. Yellowish. above closely marbled with pale purplish brown. Total length (without caudal) 72 millim.; length of head 18; width of head 18; depth of body (above base of ventrals) 12. A single specimen, from Amable Maria, Peruvian Andes, is in the British Museum. It was obtained by exchange from the Warsaw Museum, in memory of whose regretted Curator the species is named. ARGES WHYMPERI, sp. n. (Plate XLI. fig. 2.) D. 1/6. A. 1/6. P. 1/10. V. 1/4. Head as broad as long, 4 | to 5 times in the total length (caudal excluded). Eyes very small, about one fourth the width of the |