On a new Species of Bdtodns from Yorkshire. 419 



EXPLANATION OF PLATE X. Figs. 1, 1 a, 1 d. 



Fit/. 1. £iip/ic(nero2)s loni/revus, gen. et sp. n. ; the more complete side of 

 the fossil and its comiterpart (1 «), nat. size, with scale (^1 Z>) 

 enlarged ten times. — Upper Devonian ; Scaumenac Bay, 

 Province of Quebec, Canada. [British Museum.] 



c, caudal tin ; d., dorsal fin ; o., orbits. 



LVI. — On a new Species of Deltodu.s from the Lower Car- 

 boniferous [Yoredale Rocks) of Yorkshire. By A. Smith 

 Woodward, LL.D., F.L.S. ' 



[Plate X. figs. 2, 2 «, 2 5.] 



The dental plates of some of fclie Palfeozoic Cochliodont 

 sharks attain a considerable size, but those referable to the 

 genus Deltodus, as defined in the British Museum Catalogue, 

 have not hitherto been remaricable in this respect. A new 

 specimen, presented to tlie British Museum by the Rev. Addi- 

 son Crofton, M.A.^ is tlierefore of much interest as showing 

 that at least one species of J)eItodus rivalled the largest 

 species of some allied genera in size. This fossil was dis- 

 covered by the donor in a dark-coloured limestone of the 

 Yoredale Series on Blackthorn Farm, between Long Preston 

 and Slaidburn, North Yorkshire. It is shown of three 

 quarters tiie natural size from the oral and attached faces 

 and from the liinder aspect in PI. X. figs. 2, 2 a, 2 h. 



This dental plate is much inrolled at the attenuated outer 

 margin ; it is thus of tlie form commonly assumed to belong 

 to the lower jaw. If it be truly lower, it is the hinder dental 

 plate of the left mandibular ramus. Its curvature is not 

 directly at right angles to the long axis of the ramus, but 

 very oblique, so that the antero-lateral margin [a.) is much 

 longer than the postero-lateral margin {p-). Its outer in- 

 rolled portion is obscured by the matrix, but the inner 

 margin (i.) is well preserved and seen to be gently sinuous. 

 Its maximum transverse measurement at the inner margin is 

 0*06 m. The coronal surface is only gently convex and the 

 small hinder wing of the plate is not sliarply defined by any 

 depression or flattening. The upper functional portion is 

 crossed by eight or nine rounded and sinuous furrows, be- 

 tween each two of which the crown is slightly raised into a 



27* 



