1907.] ON NEW LORICARIID FISHES. 795 



5. Descriptions o£ new Loricariid Fishes from South 

 America. By C. Tate Regan, M.A., F.Z.S. 



[Received October 4, 1907.] 



(Plates XLYII.-XLIX., and Text-figures 206-208.) 



The fishes here described are a new Otocinclus, five new 

 species of Plecostomus, and two neAv species of Arges. Since the 

 pubHcation of my monograph of the Loricariidfe (Trans. Zool. 

 Soc. xvii. 1904) I have written a note* calling attention to the 

 specific distinctness of Plecostomus horriclus Kner and P. tenuicauda 

 Stdr. from P. emarginatus 0. & V., with which they had been 

 united; whilst Dr. R. von Iheringt has described four new 

 species, P. tietensis, P. regani, P. paiolinus, and P. hermanni, from 

 San Paulo, Brazil. Including the five new species described below, 

 four of which have been sent to me by Dr. von Ihering, the 

 known species of the subgenus Plecostomus (i. e., with an adipose 

 fin and without opercular bristles) now number 32, instead of 

 the 21 described in my monograph. 



Plecostomus iheringii, sp. n. (Plate XLVII. fig. 1.) 



Depth of body 4f in the length, length of head 3i. Depth of 

 head If in its length, breadth of head IjL, length of snout 1-|, 

 diameter of eye 6^, interorbital width 2 Jr. About 40 teeth on 

 each side in both jaws; length of mandibular ramus 2 in the 

 interorbital width. Barbel nearly as long as the eye. Snout 

 obtuse, narrowed anteriorly ; supraorbital ridges slightly raised ; 

 supraoccipital somewhat elevated posteriorly, but without median 

 ridge, bordered posteriorly by a single scute ; occipital process 

 short ; temporal plates, nuchal scutes and anterior scutes of the 

 second series weakly keeled. Scutes spinulose, 26 in a longi- 

 tudinal series, 6 between dorsal and adipose fin, 13 between anal 

 and caudal. Lower surface of head naked except for a granular 

 patch in front of each gill-opening ; abdomen in great part naked, 

 covered with granular scales laterally and posteriorly ; a trans- 

 verse strip of granular scales between the pectorals. Dorsal I 7, 

 the first ray a little shorter than the head, when laid back 

 extending to the third scute behind the last ray, which is ^ as 

 long as the first ; length of base of dorsal equal to its distance 

 from the posterior part of spine of adipose fin. Anal I 4. Pec- 

 toral spine extending to anterior ^ of ventral fin. Caudal 

 emarginate, the middle rays less than |- as long as the longest. 

 Caudal peduncle 2|- as long as deep. Posterior part of head with 

 transverse stripes ; fins duskj^, the dorsal with the posterior half 

 of each interradial membrane darker than the rest. 



* Ann. Maa:. Nat. Hist. (7) xvii. 1906, p. 94. 



t Ann. Mag. Nat. Hist. (7) xv. 1905, pp. 558-o61. 



I'Roc. ZooL. Soc— 1907, Xo. LIV. 54 



