1891.] ON SILUROID FISHES FROM BRAZIL. 231 



be regarded as congeneric with Thomson's or Koren and Danielssen's 

 species. Might not the second section of the generic diagnosis 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. vexUlifer 

 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 BatJiy' 

 Master ; it is not an Astropectinine, as the Astropectininee 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. 



DESCEIPTION OF THE PLATES. 

 Plate XXIII. 



Fig. 1. Bathybiaster vexUlifer 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 ambu- 

 lacral 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. The structure of the ambulacra, X 2. 



3. The form and characters of the dorsal paxillas, X 2. 



4. A view of the side of the arm, X 2. 



6. 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 Eio 

 Grande do Sul^ Brazil. By G. A. Boulenger. 



[Eeceived 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 



