Barkas — New Fish-tooth from the Coal. 495 



canoes are connected with internal lakes of molten matter : but no 

 reason that I know of has been suggested for the elongated forms 

 which these trains of volcanoes assume, frequently, as in the Andes, 

 following lines of elevation. The theory now proposed offers an 

 explanation of this fact. It also explains the intermittent nature of 

 volcanic action, and the migration of volcanic conditions to different 

 portions of the Earth's crust at successive geological epochs. 



in. — On Climaxodus, or Pcecilodus; a Palatal Tooth from 



THE Low Main Coal-Shale, Northumbejbland. 



By T. P. Barkas, Esq. 



IN the course of my recent investigations among the fauna of the 

 Low Main Coal-shale in the county of Northumberland, which 

 lies at an average depth of about 100 fathoms from the surface, I 

 have found among numerous fish and reptilian remains three spe- 

 cimens of teeth that present the appearance of being vomerine in their 

 nature. The tooth here represented in the woodcut, of the natural 

 size resembles exactly in size and form another specimen which I 

 have in my possession, the view exposed being the front aspect of 

 the tooth. I have a third specimen, which exhibits the upper or 

 attached part of the tooth ; it has a sharp curved appearance, not 

 unlike the back of a well-written letter S. 



The only reference I can find to the tooth in question is in Sedg- 

 wick and M'Coy's ''British Palaeozoic Fossils ; " in which work the 

 genus is both figured and described under the name of Climaxodus. 

 Climaxodus of M'Coy, and Pcecilodus of Agassiz are, I am informed, 

 so nearly alike, if not absolutely identical in all their leading charac- 

 teristics, that they may with propriety be, for the future, treated as 

 one genus. If such be the case, then the older name Pcecilodus, 

 given by Agassiz, ought to have the preference. But although 

 Agassiz in his " Poissons Fossiles " (vol. iii. p. 174) names the genus 

 Pcecilodus, and refers six species^ to it, none of them have been 

 either figured or described by him, and I am therefore without the 

 means of determining the generic relationship to the teeth I havefound.'^ 



Assuming that Climaxodus and Pcecilodus are identical, I adopt the 

 former name, which, although not the older, has the claim to be 

 accepted, as it is accompanied by both figure and description. The 

 following is the description of M'Coy's genus and species extracted 

 from Sedgwick and M'Coy's " British Palasozoic Fossils," p. 620. 



Genus, Climaxodus (M'Coy). 



" Gen. Char. — Tooth longer than wide, gradually narrowing to- 

 wards the front, with nearly straight sides ; anterior part of the 

 crown crossed by broad, imbricating, transverse ridges at right angles 

 to its length ; surface minutely punctured. 



" The above generic name has reference to the remarkable step -like 

 character of the ridges which cross the anterior part of the tooth at 

 regular intervals. The broad posterior part of the tooth is without 



1 P. angustus, P. Jonesii, F. ohliquus, F. parallelus, P. suhlcevis, P. transversus. 



2 Certain teeth from the Carboniferous shale of Carluke, in the British Museum, 

 have been named Fodcilodus obliquus, Agassiz. 



