COCHLIODOXTHLE. 
177 
more or less crenulated. Other side-teeth with gently rounded 
crowns and crenulated margins; symphysial teeth smaller and 
feebly prehensile. 
A considerable portion of the dentition of the type species of the 
genus has been described by It. H. Traquair 1 It appears that there 
are two forms of the large dental plates, one probably in each jaw : 
and it seems likely that there was originally at least one series of 
small teeth situated posteriorly to these. The “ upper ” dental 
plate has a relatively greater antero-posterior measurement than 
the “ lower,” and is less curved round the supporting cartilage. 
Psephodus magnus (M‘Coy). 
1843. Cochliodus magnus, L. Agassiz, Poiss. Foss. vol. iii. p. 174 (name 
only )' 
1843. Helodus planus, L. Agassiz, tom. cit. p. 173 (name only). 
1843. Helodus didymus , L. Agassiz, tom. cit. p. 173 (name only). 
1843. CocJdiodus magnus, J. E. Portlock, Rep. Geol. Londonderry, 
p. 466, pi. xiv. a. fig. 4 (figure only). 
1843. Helodus planus = Cochliodus magnus, J. E. Portlock, op. cit. p. 462. 
1855. Cochliodus magnus, F. M‘Oov, Brit. Palaeoz. Foss. p. 622. 
1$55. Helodus planus, F. M‘Coy, op. cit. p. 631, pi. 3 i. figs. 12-15. 
1855. Helodus didymus, F. M‘Coy, op. cit. p. 630, pi. 3 1 , figs. 18-20 
(in part). 
1855. Helodus Icevissimus, F. vPCoy, op. cit. p. 630 (in part). 
1855. Helodus rudis, F. M‘Coy, op. cit. p. 631, pi. 3 k. fig. 4. 
1862. Psephodus magnus, Morris & Roberts, Quart. Journ. Geol. Soc. 
vol. xviii. p. 101 (name only). 
(P) 1878. Psephodus magnus, L. G. de Iloninck, Faune Calc. Carbf. 
Belg. pt. i. p. 60, pi. iv. fig. 16 (non figs. 14, 15, 17). 
(?) 1878. Tomodus craigi, L. G. de Koninek, op. cit. pt. i. p. 61, pi. iv. 
fig. 8, pi. vi. figs. 18, 19. 
1883. Psephodus magnus, J. W. Davis, Trans. Roy. Dublin Soc. [2] 
vol. i. p. 439, pi. Iv. figs. 1-14. 
1883. Lophodus Icevissimus, J. W. Davis, tom. cit. p. 404, pi. li. fig. 18 
(in part). 
1883. Lophodus didymus, J. W. Davis, tom. cit. p. 407, pi. li. fig. 21 (in 
part). 
1883, Helodus rudis, J. W. Davis, tom. cit . p. 457, pi. lix. fig. 11. 
1883. Selachian Fish, J. Coutts, Trans. Geol. Soc. Glasgow, vol. vii. 
p. 164. 
1885. Psephodus magnus, R. H. Traquair, Trans. Geol. Soc. Glasgow, 
vol. vii. p. 392, pi. xvi.; and Geol. Mag. [3] vol. ii. p. 337, 
pi. viii. 
1886. Psephodus magnus, J. W. Davis, Geol. Mag. [3] vol. iii. p. 151. 
1 Trans. Geol. Soc. Glasgow, vol. vii. (1884), p. 396, pi. xvi. ; also Geol. Mag. 
[3] vol ii. (1885), p. 337, pi. viii. 
