496 



Barkas — New Fish-tooth' from the Coal, 



ridges, and resembles a Psammodus. In the fact of its being as it 

 were small, ridged, Psammodi, these teeth are allied to the genus 

 Foccilodus, but all the true Pcecilodi are inequilateral mussel-shaped 

 teeth, consequently placed in pairs in the mouth, and have the ridges 

 oblique ; the Climaxodi, on the contrary, are equilateral, and were 

 therefore most probably mesial in position, and the ridging is trans- 

 verse.^ I am aware of one species in the Armagh limestone, and the 

 following, Climaxodus imhricatus (M'Coy), the only specimen I have 

 access to, at jDresent, of this species, is imperfect at each end, being 

 seven lines long, five and a half lines wide at the broad end, and three 

 lines wide at the anterior end ; the anterior portion of the crown is 

 crossed by seven transverse imbricating ridges in a space of four 

 lines, the posterior ones are three-fourths of a line apart, and have a 

 double curvature arising from a small backward wave in the middle, 

 the anterior ones are closer, and pass with a slight forward curve 

 across the tooth ; all the imbrications have a backward curve at 

 their extremities, giving them the appearance of lapping round the 

 crown, and all have their free edges directed backwards, so as to 

 resemble a row of Petalodi or other shark's teeth soldered together 

 in the position they usually occupy, one behind the other; the 

 posterior half is without ridges ; the whole crown is slightly convex 

 at the sides and concave in the middle ; the surface is dull, and seen 

 by the lens to be finely punctated." 



" Position and Locality. — Eare in the dark impure limestone over- 

 lying the main Carboniferous limestone of Derbyshire." 



" The above is figured pi. iii. g, fig. 5, natural size ; fig. 5a, portion 

 of surface of ditto magnified." 



The following is a brief description of the tooth now figured (see 

 Woodcut) :— - y ^ 



Fig. 1. 



Fig. 2. 



Climaxodus ovatus, sp, nov. Low Main Coal-shale, Northumberland (Nat. size). 

 Fig. 1. View of surface of the tooth. Fig. 2, Side-view, to show elevation of crown of tooth. 



Gen. Char. Tooth longer than wide, rapidly narrowing towards 

 the back, the entire crown crossed by broad, transverse ridges at 

 right angles to its length ; surface irregular and smooth. The first 

 ridge is one-fourth the length of the tooth from its anterior part. 



1 May not these equilateral teeth have been the vomerine, and the oblique teeth, 

 called Fuicilodus, have belonged respectively to the right and left rami of the lower 

 jaw of the same fish, their structure and general similarity of form being the same ?— 

 Ed. Geol. Mag. 



