J. W. Davis — Carboniferous Fish-remains. 149 



The fauna of this district affords some features of peculiar interest. 

 There is an entire absence of fin-rays, and of the sharply-pointed 

 couical teeth like Cladodus, a negative evidence of their intimate 

 relationship where present. There are two genera of Petalodontidaa, 

 three of the Copodontidse, five of the Cochliodontidae, one of Pleu- 

 rodus and one of Psammodns. Of all these only one species, Psephodus 

 magnus, Agass., has been previously recorded from Derbyshire. 

 Besides P. magnus, the following fish-remains have been chronicled 

 either in M 'Coy's British Palaeozoic Fossils, or in the Fossil Fishes 

 of the Carboniferous Limestone series of Great Britain, in the Trans- 

 actions of the Royal Dublin Society, by the present writer : — 



Acondylacantlms {Lept acanthus, M'Coy) Deltodus aliformis, Agass. 



juneeus, M'Coy. Deltoptychius acutus, Agass. 



Cladodus mirabilis, Agass. Tcecilodus foveolatus, M'Coy. 



Cladodus striatus, Agass. Petalodus acuminatus, Agass. 



Pristieladodus dentatus, M'Coy. Cheirodus pes-rance, M'Coy. 

 Tetrodus patelliformis, M'Coy. 



To this list is now added twelve species, five of which have not 

 previously been described ; they are comprised in the following 

 descriptions, to which are added such observations as appear necessary 

 to indicate peculiarities of form or structure. 



Family Petalodontid^, Newberry and Worthen. 

 Genus Petalodus, Owen. 



Owen, Odontography, p. 61 (1840). 



Davis, Trans. Roy. Dublin Soc, n.s. vol. i. p. 429 (1883). 



Petalodus Hastingsice, Owen. 

 Odontography, p. 61, pi. xxii. figs. 3, 4, 5. 

 Davis, I.e. p. 493, pi. lix. figs. 16-21. 



A considerable number of the teeth of this species have been found 

 varying in size as well as in form. An average tooth apparently of 

 full size is 0-35 inch across the crown : the height of the latter being 

 0-15 inch. The base is nearly double the height of the crown. 

 Whilst agreeing generally in form with the species from the Mountain 

 Limestone of Armagh, it differs in the greater area occupied by the 

 imbricating ridges at the base of the crown ; whilst the former 

 possess five or six folds or ridges, the specimens from Derbyshire 

 have nine. Some of the examples are broader across the crown, 

 than the average tooth already named, and the height of the crown 

 is less, very thin, and almost straight. This may be due to greater 

 wear, the coronal surface being reduced from the normal convexity 

 to a more or less straight edge ; or, it may indicate a different species. 

 The broad form closely resembles in some particulars the specimens 

 of Petalodus inequilateralis from the Limestone of Wensleydale. 



Genus Petalorhynchus, Agass. MS. 

 Davis, Trans. Roy. Dublin Soc. n.s. vol. i. p. 516 (1883). 

 Petalorhynchus psittacinus, Agass. MS. 

 Davis, I.e. p. 516, pi. lxi. figs. 12-16. 

 Hitherto the teeth of this species have been found only in the 

 Mountain Limestone at Armagh and the Carboniferous Series near 



