100 
8ELA.CHII. 
root much thicker than the crown, and readily detached from the 
latter. Coronal surface generally marked by transverse rugee. The 
exterior postero-lateral angle of each tooth is somewhat produced 
backwards, to ensure more firm articulation with the succeeding 
tooth ; and there appear to have been not more than four antero- 
posterior rows in each jaw — a middle pair and a lateral, without 
any median azygous series. 
Psammodus ragosus, Agassiz. 
1838. Fmmmodus rugosus, L. Agassiz, Poiss. Foss. vol. iii' P- 
pi. xii. figs. 14-18, pL xix. fig. 16. _ _ 
1838. Psammodus poroma,h.A.^ss\z,t(y)n.cit.Tg. 112 , pi. xiii. figs. 
1843. Psammodus nigosrn, J. E. Portlock, Rep. Geol. Londonderry, 
p. 406, pi. xiv a, fig. 1. ■ -2 
1843. Psammodus porosus, J. E. Portlock, op. cit. p. 466, pi. xiv a, 
1844. Psammodus rugosus, L. G. de Koninck, Descr. Anim. Foss. err. 
Garb. Belg. p. oio, pi. Iv. fig. 4. ... ^ g 
1844. Psammodus x>orosus, L. G. de Koninck, op. cit. p. 016, pi. hii. • 
1848. Psammodus canal icidatus, F. M'Coy, Ann. & Mag. Nat. Hist. 
vol. ii. p. 122. o 
1855. Psammodus catudicidatus, F. M'Coy, Brit. Paleeoz. Foss, p- > 
pi. 3 a, fig. 12. 
1866. Psammodus rugosus, F. M'Coy, op. (At. p. 044. 
1866. Psammodus ntgosus, var. porosus, F. M'Coy, op. cit. p. 644. 
1800. Psammodus porosus, E. d’Eichwald, Lethaea Rossica, 'vo . i- 
p. 1647. 
1862. Psammodus rugosus, Morris & Roberts, Quart. Journ. Geol. Soc. 
vol. xviii. p. 102. 
1864. Psammodus ntgosus, II. Romanowsky, Bull. Soc. Imp. 
cou, pt. ii. p. 168, pi. iii. figs. 3, 5. - fi 4 
1864. Psammodus porosus, II. Romanowsky, tom. cit. p. 168, pi. in- ' 
1875. Psammodus porosus, W. II. Baily, Figs. Char. Brit. Foss. p. > 
pi. xli. fig. 9. 
1877. Psammodus rugosus, R. Etheridge, jun., Geol. Mag. [3] vo ■ i''- 
p. 308, pi. xiii. figs. 7-9. . 
1878. Psammodus porosus, L. G. de Koninck, Faune Calc. Carb. leg- 
pt. i. p. 41, pi. V. figs. 1-6. I 
1883. Psammodus rugosus, J. W. Davis, Trans. Roy. Dublin boo. [ J 
vol. i. p. 4.69, pis. Ivi., Ivii. , 
1884. ilsam»iorf!«r«(7osMs, .T. W. Davis, Quart. Joum. Geol. Soc. vol. 
p. 029. 
1880. Psammodus rugosus, J. W. Davis, Geol. Mag. [3] vol. iii. P- 
Ti/pc. Detached teeth ; Bristol and British Museums. 
A very largo species. Teeth comparatively thick ; the coronal 
surface in unworn specimens marked by numerous strong, coarse. 
