2 Mr. F. M'Coy on some new Fossil Fish 



examine at leisure. To Mr. Griffith of Dublin I am also indebted 

 for the loan of some interesting forms from the lower carboni- 

 ferous shales of Ireland. The Rev. W. Stokes of Caius College, 

 Cambridge, allowed me to select a large suite of new and inter- 

 esting forms from his Armagh collections, and having given me 

 the opportunity of drawing and describing them, they were de- 

 posited in the collection of that University, whence I have also 

 described a few species from the Derbyshire limestones collected 

 by Mr. W. Hopkins, F.G.S. &c. To the Rev. Prof. Clark of 

 Cambridge, and also to Mr. Anthony of Caius College, Cam- 

 bridge, I am infinitely indebted for the use of their magnificent 

 microscopes, and for the kindness with which they took the 

 trouble to make microscopic sections for me of the new genera ; 

 without their most valuable aid I could not have presented the 

 internal microscopic structure of those forms. 



CffiLACANTHI. 



Holoptychius (Ag.). 



When we look to the large number of species of this genus now 

 known in the old red sandstone, all characterized by thick, bony 

 longitudinally plaited scales, and the largest of them having but 

 small conical teeth, sulcated at the base, and then compare them 

 with those large compressed teeth in the carboniferous shales, such 

 as the H Hibberti (Ag.), of which Prof. Owen formed his genus 

 Rhizodus, and the nearly allied, if not identical, H. Portlocki (Ag.) 

 of the Irish shales, with their associated large, thin, rotundo- 

 quadrate scales having the minute reticulated structure of Gly- 

 ptolepis, I think it would be desirable, instead of considering the 

 genera Holoptychius and Rhizodus synonymous as they are now 

 held, to retain both generic names, but restricting each to such 

 forms as those above noticed. In this point of view the follow- 

 ing is the only true Holoptychius I have yet seen from the car- 

 boniferous limestone. 



Holoptychius Hopkinsii (M'Coy). 



Sp. Char. Scales elongate, narrow, elliptically pointed, very thick, 

 convex ; exposed portion strongly enamelled, covered with nu- 

 merous thick, rounded, slightly fiexuous, anastomosing, longi- 

 tudinal ridges; concealed smooth portion deeply bifurcate, 

 generally bent laterally at a considerable angle with the ex- 

 posed portion. Length of enamelled portion 6 lines, width 3 

 lines. 



The thick, narrow form and strong longitudinal ridges of the 

 surface distinguish this species easily from its congeners. It 



