148 



Poivrie — On the Genus Cheirolepis. 



hension of the true nature of a series of elongated plates, situated 

 below the lower jaw, which seem peculiar to this genus. The many 

 poiuts in which it very widely differs from the Acanthodeans in- 

 duced the late Hugh Miller to suggest its removal altogether from 

 them ; and a distinct family, which he names Cheirolepini, is formed 

 for its reception by Pander. Professor Huxley, in his Introductory 

 Essay on the classification of the Old Eed Sandstone Fishes, in the 

 Tenth Decade of British Organic Eemains, published in connexion 

 with the Geological Survey, perhaps the most useful contribution yet 

 made towards elucidating their nature and affinities, fully agrees with 

 Pander, in the necessity of this step, and indicates, for the reasons 

 there stated, the probability of its being " the earliest known form of 

 the great sub-order, the Lepidosteida." Prof. Huxley, however, 

 states that " the opercular apparatus and the Branchiostegal rays were 

 not observed by Pander, nor have I seen indubitable evidence of 

 their characters ; " but, seemingly, trusting to the accuracy of Agassiz's 

 description, in narrating the points in which it diverges from the 

 sub-order Crossopterygidce, he enumerates as one, its possessing " no 

 jugular plates." In this he seems to me in error, some specimens in 

 my possession showing, what I can consider only to be, true 

 principal and lateral jugular plates, although certainly not so 

 distinctly preserved as in most of the Old Ked Sandstone genera 

 having these appendages. 



Pig. 1.— Diagram of Head-plates of Cheirolepis (ventral aspect). 



In Cheirolepis the head is undoubtedly covered by osseous plates, 

 being somewhat similar in this respect to Osteolepis, Diplopterus, etc., 

 but in all specimens I have yet examined these are so imperfectly 

 preserved, and so much displaced, that the true form and relative 



