24 PISH OF THE CARBONIFEROUS PERIOD. 



Climaocodus imbricatus (M'Coy). 



The only specimen I have access to at present of this species 

 is imperfect at each end^ being 7 lines long, 5^ lines wide at the 

 broad end, and 3 lines wide at the narrow anterior end ; the an- 

 terior portion of the crown is crossed by 7 transverse imbrica- 

 ting ridges in a space of 4 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 punctured, 



Rare, in the dark impure limestone overlying the main carbo- 

 niferous limestone of Derbyshire. 



{Col. University of Cambridge.) 



Pcecilodus aliformis (M^Coy). 



Sp. Char. Wing-shaped or contorto-subtrigonal, narrow before, 

 broad and subtruncate behind ; inner, straight margin thin, 

 higher in the middle than at each end, the surface seeming 

 concave from thence to the external oblique margin, which is 

 abruptly deflected, much thickened, rounded, strongly arched 

 downwards at each end, with a slight sigmoidal curve ; this 

 ridge is crossed by seven or eight large, obtusely rounded 

 wrinkles, which become obsolete as they approach the thin 

 inner margin ; surface finely granuloso-punctate under the 

 lens. 



This species most resembles some of the wing-shaped forms 

 of the P. suhlcevis (Ag.), but the whole tooth is more strongly 

 contorted sigmoidally; the external obHque margin is more 

 thickened, ridge-like and deflected, and above all the great size 

 of the transverse waves or wrinkles easily distinguishes it. The 

 length of a perfect specimen is 1 inch 3 lines, width of the broad 

 posterior end 9 lines, depth of the middle of the external margin 

 4 lines, width of the transverse wrinkles rather more than 1^ line. 



Rare, from the black upper limestone of Derbyshire. 



[Col. University of Cambridge.) 



Poecilodus foveolatus (M'Coy). 

 Sp. Char. Longitudinally clavate, depressed, nearly three times 



