206 
SELACHII. 
Owen ' has stated that there is evidence of a third smaller dental 
j)lato in advance of those just described ; but 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 i)robablo that there was no such triangular plate, but 
rather a series of small llelodusAiko teeth. 
Cochliodus contortus, Agassiz. 
1838. Cochliodm contortus, L. Agassiz, Poiss. Foss. vol. iii. p. 115, 
pi. xix. fig. 14 {non pi. xiv. figs. 16-33). 
1840. Cochliodus contorttm, K. Owen, Odontography, vol. i. p. 62, 
vol. ii. p. 10, pi. xxii. lig. 1. 
1855. Cochliodus contortus, F. M'Coy, Brit. Palajoz. Foss. p. 622. 
1856. Cochliodus contortus, F. lloemer, in Bronii’s Leth. geogn. vol. i. 
p. 708, pi. ix. b. fig. 4. 
1807. Cochliodus contoHus, 11. Owen, Gool. Mag. vol. iv. p. 69, pi. iii. 
__figs. 1, 3, 4,5. 
1867. Tomodus convexus, R. Owen, t<nn. cit. p. 62, pi. iv. figs. 2-5. 
1878. Cochliodus contortus, L. G. de Koninck, Fauue Calc. Coi'bf. Belg. 
pt. i. p. 57, pi. vi. fig. 14. 
1883. Cochliodus contortus, J. \V. Uavis, Trans. Roy. Dublin Soc. [2] 
vol. i. p. 421, pi. Iii. figs. 1-6. 
Ti/ 2 >e. Dental plates in natural position upon the jaw ; British 
Museum. 
The typo s])ecic8. Dental plates very variable in form, the pro- 
portions ot the antero-lateral and postero-latcral 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. 
None of the dental plates from Bristol assigned by Agassiz (mi. 
cit. pi. xiv. figs. 16-33) to this species can bo correctly retained in 
this i)osition. Tho specimens described by Owen were from 
Armagh, not from Bristol, as stated. Some Russian teeth, also 
ascribed to Cochliodus contortus by Romanowsky (BuU. Soc. Imp. 
Nat. Moscou, 1864, pt. ii. p. 159, pi. iii. figs. 7-10), are very 
ijuestionably determined. 
I'orni. IjOC. Lower Carboniferous Limestone : Armagh, Ire- 
land ; Belgium. Upper Cai'boniferous Limestone : Yorkshire, 
England; Belgium. 
* Geol. Mag. vol. iv. 1867, p. GO. 
