116 Proceedings of the Royal Physical Society. 



measures. But specimens which are at all entire are rare ; 

 indeed, it is only in the North Staffordshire district that any 

 number of specimens approaching completeness have been 

 found. 



Three species of carboniferous Acanthodians have been 

 described, and these are usually referred either to the genus 

 Acanthodes of Agassiz, or to Acaiithodopsis of Hancock and 

 Atthey. And here the question as to genus is of very great 

 interest. The genus Acanthodes was instituted by Agassiz 

 to include these forms, in which, as in the type species A. 

 Bronnii of the Lower Permian of Lebach and Saarbriicken, 

 there are, besides the pectoral spines, two ventral, one dorsal, 

 and one anal, all supporting their respective fins, and the 

 dorsal being situated behind the anal one. In this category 

 the following species have been included : From the Old Eed 

 Sandstone of Scotland — A. pitsillus, Ag., A. Peachii, Egert., 

 A. corrugatus, Egert., and A. Mitchelli, Egert.; from the 

 carboniferous formation — A. sulcatus, Ag., and A. JVardi, 

 Egert. ; and from the Lower Permian of Germany — A. 

 Bronnii, Ag., and A. gracilis, Beyrich. By Agassiz the teeth 

 are stated to be ''fines," and " disposees en une simple rangie; " 

 and in A. pusillus he describes the mouth as being " garnie de 

 tres petites dents qui meme sous une tres-forte loupe ne paraissent 

 que comme de petits points noirs." * Troschel could, however, 

 find no certain evidence of teeth at all in A. Bronnii, nor 

 Eoemer in A. gracilis ; but on the other hand, Kner describes 

 both jaws in the former species as bearing "feine kleine Spitz- 

 zdhne in ziemlich dichter Reihe" in this respect corroborating 

 the statement of Agassiz as to A. pusillus. 



Messrs Hancock and Atthey, however, drew attention in 

 1868 to certain peculiar dentigerous bones, or jaws, which 

 are not uncommon in the shale overlying the " Low Main" 

 coal seam at Newsham, near Newcastle-on-Tyne.f Each of 

 these bears five or six large triangular-looking teeth, laterally 

 compressed, confluent at their bases, and having their sur- 



* Poissons Fossiles du vieux Gr^s rouge, p. 35, 36. 



t "Notes on the Remains of some Reptiles and Fishes from the Shales of 

 the Northumberland Coal Field," Ann. and Mag. Nat. Hist. (4), vol. i., 

 pp. 364-368. 



