Section IV., 1885. [ 107 J Trans. lioY. Soc. Canada, 



VI. — On the Skull and Audi'o^nj Orrjan of the Slluroid Hypoi>hthalmus. 

 By E. Eamsay Wright, University College, Toronto. 



(Read May 25, 1885 ) 



The group of fishes generally ranked as the family SUuridcc still offers a wide field to 

 the comparative anatomist, notwithstanding the numerous investigations which their 

 bizarre appearance and singular anatomical features have invited. Although, as observed 

 by Professor Gill, (No. 2, p. xlv), the group is really a natural one and strongly contrasts 

 with any other, there is no other " family" of Teleosts in which such wide limits of struc- 

 tural difference exist. As these differences are such as are considered of family value in 

 other cases, there can be no cjuestion of the desirableness of expressing this in a system of 

 classification, by assigning to the Siluroids a higher than family rank. This appears to be 

 recognized by those ichthyologists who have adopted Professor Cope's ordinal name, 

 NematognalM, for the group. Giiuther's subdivision of the Siluroids rests primarily on the 

 development and position of the rayed dorsal fin. He distinguishes eight sub-families 

 and seventeen groups. Cop3 recognizes three families in the order Nematognathi, viz . the 

 Siluridœ, Asprediuidœ, and Hypophthalmidœ ; while Gill separates from Cope's Siluridœ 

 eight aberrant types under distinct f\xmilies, using the term SUuridcc in a narrower sense, 

 for the forms embraced under Giinther's sub-families, S. heteroplerœ, proieropterœ, and sleno- 

 branchiœ. 



Our North American fresh waters contain some thirty species, ranged under the 

 genera Noturus, Lepfops, Gronias, Amiunis, and Idahirus, all of which are closely related and 

 belong to the sub-family S. proieropterœ and group Bagrina of Giinther. The anatomy of 

 the cat-fishes constituting this very homogeneous section has been sufficiently illustrated 

 in the "Contributions to the Anatomy of Amiurus," published by myself and some former 

 pupils, but much remains to be done in regard to the forms with which the tropical fresh 

 waters of the Old and New Worlds teem. 



One of the little known Siluroid types is the Brazilian genus H//pojihthnliii>is, Spix ; of 

 one species of which H. marginatus, Cuv. et Val., I have recently had the opportunity of 

 studying two specimens throi^gh the kindness of Professors B. G. Wilder and Alex. Agassiz. 



Ichthyologists are familiar with the fact that Hypophthalmus has been accorded a 

 somewhat isolated i^osition among the Siluroids on account of the (supposed) absence of 

 the air-bladder and non-fusion of the anterior vertebrae. Thus Giinther (No. 4) forms for 

 the genus a distinct sub-family and group, mentioning as its essential characteristic that 

 " the anterior vertebrte are not iinited into one." 



Again, Cope (No. 1, p. 331) establishes for the genus one of three families, into, which 

 he divides the Nematognathi, and recognizes the great morphological importance of the 



