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Show 1891.] ON SILTJROID FISHES F R O M BRAZIL. 231 be regarded as congeneric with Thomson's or Koren and Danielssen's species. Might not the second section of, the generic diaguosis run thus ? : " 5-rayed, with an extremely wide ambulacral furrow, some of the bounding spines of which bear vexilla" ? The diagnosis goes on, " The interbrachial space broad and closely beset with sessile pedicellarise." I cannot from the figure given regard B. pallidus as having a broad interbrachial space, and B. vexillifer certainly has not; there is nothing in the dried specimen to justify our speaking of the scales which thickly cover this area as pedicellarise, but I am not entitled to traverse Messrs. Koren and Danielssen's description ; I would suggest that the lines run " The interbrachial space closely covered with pedicellaria-like scales." I am by no means sure that B. loripes, Sladen, is a true Bathybiaster ; it is not an Astropectinine, as the Astropectininse are defined by Mr. Sladen; the ambulacral ossicles are set at an angle and not side by side, and the groove is not nearly so wide as in the two northern species. Individual Peculiarity.-Here and there two superomarginals, apparently separated only in their upper half, correspond to one inferomarginal. DESCRIPTION OF THE PLATES. P L A T E XXIII. Fig. 1. Bathybiaster vexillifer from above, to show the general form and appearance of the specimen. 2. The same from below, to show particularly the great width of the ambulacral grooves. Both three fourths the natural size. PLATE XXIV. Fig. 1. A " vexillum," X 20. a, The dried membrane attached to the spine shown in situ, as seen in the dried specimen. 2. Tbe structure of the ambulacra, X 2. 3. The form and characters of the dorsal paxilla?, X 2. 4. A view of the side of the arm, X 2. 5. The mouth-plates and adjoining ossicles, X 2. 6. The region of the anus, X 4. 4. An Account of the Siluroid Fishes obtained by Dr. H. von Ihering and Herr Sebastian Wolff in the Province Rio Grande do Sul, Brazil. By G. A. BOULENGER. [Received March 21, 1891.] (Plates XXV. & XXVI.) During the last few years, the British Museum has received a great number of Fishes collected in the Province Rio Grande do Sul by Dr H. von Ihering and Herr Sebastian Wolff. The recently published excellent synopsis of the American Siluroids by Dr. and |