206 
SELACHII. 
Owen 1 has stated that there is evidence of a third smaller dental 
plate in advance of those just described; hut the original specimen 
supposed to prove this circumstance merely shows the remains of 
bases of teeth in the position indicated, and more recent discoveries 
render it probable that there was no such triangular plate, but 
rather a series of small Heloclus -like teeth. 
Cochliodus contortus, Agassiz. 
1838. Cochliodus contortus, L. Agassiz, Poiss. Foss. vol. iii. p. 115, 
pi. xix. fig. 14 (non pi. xiv. figs. 16-33). 
1840. Cochliodus contortus, It. Owen, Odontography, vol. i. p. 62, 
vol. ii. p. 10, pi. xxii. fig. 1. 
1855. Cochliodus contortus, F. M‘Coy, Brit. Paheoz. Foss. p. 622. 
1856. Cochliodus contortus, F. Boemer, in Bronn’s Leth. geogn. vol. i. 
p. 703, pi. ix. o. fig. 4. 
1867. Cochliodus contortus, B. Owen, Geol. Mag. vol. iv. p. 59, pi. iii. 
figs. 1, 3, 4,5. 
1867. Tomodus convexus, B. Owen, tom. cit. p. 62, pi. iv. figs. 2-5. 
1878. Cochliodus contortus, L. Ct. de Koninck, Faune Calc. Carbf. Belg. 
pt. i. p. 57, pi. vi. fig. 14. 
1883. Cochliodus contortus, J. W. Davis, Trans. Boy. Dublin Soc. [2] 
vol. i. p. 421, pi. Iii. figs. 1-6. 
Type. Dental plates in natural position upon the jaw; British 
Museum. 
The type species. Dental plates very variable in form, the pro¬ 
portions of the antero-lateral and postero-lateral areas of the 
posterior plate on each side of the ridge especially inconstant. 
Large ridge gently rounded, oblique, attaining the inner margin, 
where it is broadest; coronal surface smooth. 
Bone of the dental plates from Bristol assigned by Agassiz (tom. 
cit. pi. xiv. figs. 16-33) to this species can be correctly retained in 
this position. The specimens described by Owen were from 
Armagh, not from Bristol, as stated. Some Bussian teeth, also 
ascribed to Cochliodus contortus by Bomanowsky (Bull. Soc. Imp. 
Bat. Moscou, 1864, pt. ii. p. 159, pi. iii. figs. 7-10), are very 
questionably determined. 
Form. § Loc. Lower Carboniferous Limestone : Armagh, Ire¬ 
land ; Belgium. Upper Carboniferous Limestone : Yorkshire, 
England; Belgium. 
1 Geol. Mag. vol. iv. 1867, p. 60. 
