152 J. W. Davis — Carboniferous Fish-remains. 



of P. magnus in form ; the latter are more or less pentagonal or 

 rounded, whilst this species is four-sided, two being so much longer 

 than the others as to assume almost a triangular appearance. I have 

 ventured to distinguish the species by giving it the name Psephodus 

 simplex. 



Genus Deltopty chins, Agass. MS. 

 Davis, Trans. Roy. Dublin Soc. n.s. vol. i. p. 432 (1883). 

 DeltoptycMus plicatus, Davis. 

 Quart. Journ. Geol. Soc. vol. xl. p. 628, pi. xsvi. figs. 13, 14 (1884). 

 Several teeth of this species have been obtained. They do not 

 materially differ from those described in the paper referred to above, 

 from the Yoredale Series of Wensleydale, in the possession of Mr. 

 Home ; like them, they are readily distinguished from the type 

 species of Agassiz, D. acutus, by the greater prominence of the ridges 

 occupying the surface of the crown ; the more regular and broader 

 form ; and more widely expanded outer margin. The Derbyshire 

 specimens are slightly larger than those found at Wensleydale. They 

 are delicately and beautifully punctate on the surface. 



Genus Pcecilodus, Agass. MS. 



Davis, Trans. Roy. Dublin Soc. n.s. vol. i. p. 441 (1883). 



Pcecilodus Jonesii, Agass. MS. 



Davis, Trans. Eoy. Dublin Soc. n.s. vol. i. p. 442, pi. liii. fig. 20-23. 



Teeth of this genus have been found. They correspond with 

 those of the same species found at Armagh in essential characters. 

 They are of two forms, the larger posterior tooth is about 0-5 inch in 

 breadth, the length equalling half the breadth. The posterior por- 

 tion of the tooth is broadest and is free from ridges. Its surface is 

 considerably worn and forms a concave depression. The remainder 

 of the crown is traversed by 7 or 8 parallel ridges. The whole is 

 enamelled and punctate. The second tooth is smaller, sub-triangular 

 in outline ; its length is the same as that of the larger tooth, 0*25 

 inch; the greatest breadth is 04 in., diminishing towards the opposite 

 extremity. Five ridges are exposed, extending transversely across 

 the surface, separated by somewhat deep grooves. It is similarly 

 enamelled and punctate to the posterior tooth. 



The only species of the genus Pcecilodus hitherto recorded from 

 the Mountain Limestone of Derbyshire is P. foveolatus, M'Coy 

 (British Palaeozoic Fossils, p. 639, pi. 3g). The type is in the 

 Woodwardian Museum, Cambridge, and is unique. It is readily 

 distinguished from the specimens in Mr. Parker's collection by its 

 large size, narrow, elongate form, more numerous and diagonally 

 disposed ridges, and the regular rows of puncta which run parallel 

 with the ridges. The species, Pcecilodus Jonesii, named by the late 

 Prof. Agassiz, and described in the memoir cited above, has hitherto 

 been found only in the Limestone of Ireland. It comprises teeth of 

 two forms originally considered by Agassiz to represent two species, 

 but proved by specimens in the collection of the Earl of Enniskillen, 

 now transferred to the Natural History Museum, Cromwell Eoad, to 



