THE 



aEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE III. VOL. II. 



No. VIII.— AUGUST, 1885. 



I. — On a Specimen of Psephodus magnus, Agassiz, fkom the 

 Carboniferous Limestone of East Kilbride, Lanarkshire.^ 



By R. H. TRAaTJATR, M.D., F.E.S., F.G.S. 



(PLATE VIII.) 



N his " Tableau generale des Poissons Fossiles," published in 



I 



1844, and appended to the first volume of his great work, 

 Agassiz enumerates five species of his Carboniferous selachian genus 

 CocJiliodus, of which he only described one, the well-known C con- 

 tortus ; the others, of which the names only were then published, 

 being C. magnvs, C. acutus, C. ohlongus, and C. striatus. 



C. magnus was, however, figured by Lieut.-Col. Portlock in his 

 " Geological Eeport of Londonderry and parts of Tyrone and 

 Fermanagh" (pi. 14a., fig. 4). It is a large, broadly oblong convex 

 crushing tooth, with crenulated edges, common at Armagh, in 

 Ireland, and not at all rare in the Carboniferous Limestone of many 

 localities in Scotland. In the same work (p. 462) Col. Portlock 

 quotes a letter from Captain Jones, in which that gentleman, a 

 zealous collector of fossils from the Armagh limestone, expresses the 

 opinion that this tooth passes into Helodus planus, another Armagh 

 species, named but not described by Agassiz. 



Both Cochliodus magnus and Helodus planus were described, and 

 the latter also figured, by M'Coy, who still retained them as 

 belonging to separate genera and species, for though he mentions 

 Captain Jones's opinion regarding them, he states that he himself 

 had not seen the passage. As regards C. magnus, M'Coy assigned 

 three teeth to each ramus of the jaw, so as to form an arrangement 

 corresponding with that in C. contortus. He also doubted the position 

 of the species in the genus CorUiodus, on account of the slight 

 enrolment, the little definition of the characteristic oblique ridges, 

 and the strong crenulation of the edges.^ 



Agassiz, having visited Great Britain again in 1859, extensively 

 revised the names of the Carboniferous selachian remains in the 

 magnificent collection of the Earl of Enniskillen, at Florence 

 Court, in Ireland, and instituted a great number of new generic 

 and specific names, involving in many cases considerable subdivision 

 of former genera. A list of these MS. names was supplied by 



1 Reprinted from the Transactions of the Geological Society of Glasgow, vol. vii. 

 part 2, pp. 392-402, pi. xvi. Glasgow, July, 18^o. 



2 " British Palaeozoic Fossils," London and Cambridge, 1855. 



DECADE III. — YOL. II.— NO, VIII. 22 



