56 
SELACHII. 
41204. Four teeth; Newcastle-on-Tyne. 
Presented by T. P. BarJcas, Esq,, 1868. 
P. 5289. Two teeth; West Cramlington, near Newcastle-on-Tyne. 
Presented by Sir Pickard Owen , K.C.B., 1884. 
34998-9, P. 5169. Four teeth; Upper Coal-Measures (New Iron¬ 
stone—Rag-mine), Fenton, North Staffordshire. 
Purchased. 
P. 1456. Four teeth ; Fenton. Egerton Coll. 
P. 3017-19. Eight teeth; Fenton, Enniskillen Coll. 
P. 1457. Impression of tooth very similar to those of this species ; 
Coal-Measures, Nova Scotia. Egerton Coll. 
Teeth slightly differing from those of C. pectinatus are described 
from the Coal-Measures of Nova Scotia under the name of Cteno- 
ptyckius cristatus, J. W. Dawson, Acadian Geology, 3rd edit. 1878, 
p. 209, woodcut. It is possible that the imperfect fossil last named 
(P. 1457) may be truly referable to this species. 
With Cattopristodus may also be placed the unique tooth from the 
Northumbrian Coal-Measures, described under the name of Cteno- 
ptychius aciculatus by W. J. Barkas, Monthly Rev. Dental Surgery, 
vol. ii. (1874), p. 533, figs, xxiv.-xxvi. 
Genus POLYRHXZODUS, McCoy. 
[Ann. & Mag. Nat. Hist. [2] vol. ii. 1848, p. 125.] 
Syn. Dactylodus, Newberry & Worthen, Pal. Illinois, vol. ii. I860, 
p. 33. 
Teeth very robust, with crown but slightly elevated and more 
adapted for crushing than cutting. The edge of the crown is 
generally sharp, but rarely crenulated ; its base is marked by one, 
two, or three ridges. The root is large, and deeply divided into 
several distinct, root-like lobes or fangs. 
No teeth of Polyrkizodus have hitherto been discovered in natural 
association, and it is thus impossible to distinguish between specific 
characters and the variations exhibited by the teeth in different 
parts of a single jaw. It seems certain that most of the so-called 
specific differences belong to the latter category; but since the 
various types have unfortunately received names, and as there is 
yet no absolute proof of their pertaining to one or any definite 
number of species, it is considered convenient to adopt this pro¬ 
visional arrangement. 
