176 
SELACHII. 
1884. Pleurodus zooodi, L. W. Davis, Quart. J ourn. Geol. Soc. vol. xl. 
p. 624, pi. xxvii. figs. 14-17. 
1886. Pleurodus icoodi , J. W. Davis, Geol. Mag. [3] vol. iii. p. 156. 
Type. Detached dental plates; Eeed Collection, York Museum. 
Axial carina of the dental crown narrow, rounded, divided by 
transverse sulci, corresponding to the divisions between the incom¬ 
pletely coalesced components ; lateral notches very deep. 
The dental plates of this species were first described by AY. J. 
Barkas, but were not figured until 1883, when J. AY. Davis proposed 
the name by which the species is now known. 
Form. Log. Upper Carboniferous Limestone : Yorkshire and 
Derbyshire. 
P. 4887. Eight dental plates ; Yoredale lloc-ks, Wensleydale, York¬ 
shire. Horne Coll. 
P. 5357. An abraded dental plate, probably referable to this species ; 
Ticknall, near Melbourne, S. Derbyshire. Wilson Coll. 
Dental plates of a species of Pleuroplax , from the Lower Car¬ 
boniferous Limestone of Belgium, have been described under the 
name of Tomodus laciniatus, L. G. de Koninek, Eaune Calc. Carbf- 
Belg. pt. i. (1878), p. 61, pi. vi. fig. 20. 
Genus FSEPHOBUS, Agassiz. 
[Morris and Roberts (ex Agassiz, MS.), Quart. Journ. Geol. Soc. 
vol. xviii. 1862, p. 101 h] 
Syn. Helodus, L. Agassiz, Poiss. Foss. vol. iii. 1838, p. 104 (in part). 
Lophodus , H. Romanowsky, Bull. Soc. Imp. Nat. Moscou, vol. 
xxxvii. pt. ii. 1861, p. 160. 
Aspidodus, Newberry A AAYrtlien, Pal. Illinois, vol. hi. 1866, 
p. 92. 
Tceniodus , St. John & Worthen, Pal. Illinois, vol. vii. 1883, p. 75 
(in part). /Ww Q&rr**-*? 1$ S 1 ?. ,7. 3;. £ 
At least one series of the teeth upon each ramus of the jaw repre¬ 
sented by a large gently curved plate, quadrangular, without coronal 
ridges or any marked inrolment of the outer border, and having at 
least the antero-lateral and postero-lateral margins of the crown 
1 The name only is here mentioned and applied to the species previously 
described and figured by M’Coy and Portlock under the name of Cochl-iodus 
magnus. The type species being thus already well-defined in 1862,. the generic 
name is generally regarded as dating from that year. 
