160 
BELACHII. 
1839. Ptychodui mortoni (Mantell MS.), S. Q. Morton, Joum. Aca 
Nat. Sci. Philad. vol. viii. p. 216, pi. xi. fig. 7. 
1843. Ptyehodm mortoni, L. Agassiz, Poiss. Foss. vol. iii. P- 1 > 
pi. XXV. figs. 1-3. _ 
1868. Ptyehodm mortoni, J. Leidy, Proc. Acad. Nat. Sci. Philad. p. 
1887. Ptyehodm mortoni, A. S. Woodward, Quart. Journ. Geol. oc. 
vol. xliii. p. 130. 
Type. Detached tooth. 
Teeth similar in form to those of the typical species of Ptyehodm, 
hut differing in having the centre of the crown raised into a sharp 
point, from which strong branching ridges diverge ; the broa 
marginal area is marked with an almost reticulate ornament. ^ 
The tooth from the English Chalk referred to this species y 
Dixon ' is at present doubtfully determined. 
Form. ^ Loo. Cretaceous : Alabama, TJ.S.A. ; also Niobrara re- 
taceous of Kansas {Cope). 
28394. Tooth described and figured by Agassiz, loo. cit. ; Alab^a- 
Mantell Coll- 
35586-9. Four detached teeth, one being perfect and unworn, the 
others worn at the apex ; Alabama. _ 
Presented by Prof. J. W. Mallet, 
P. 1381. Two detached teeth, one exhibiting perfectly the super^ial 
coronal markings ; Alabama. Egerton o 
P.2687. Eleven detached teeth. One is of very large size, measuring 
0-05 in breadth. Alabama. Enniskillen Coil. 
Whole or fragmentary teeth of Ptyehodus, from which the coronal 
layer of gano-dentine has been broken away by post-mortem abrasion, 
are sometimes discovered in the Chalk. One of these forms the type 
of Aulodus ayassizi^, and the two following specimens are so 
figured by Dixon as “ Nascent teeth of Ptyehodus.” 
28350. Abraded tooth, figured in Dixon’s Foss. Suss. pi. 
fig. 5 ; Chalk, Sussex. 
39124. Large abraded tooth, figured op. cit. pi. xxx. fig. 4 ; Chalk, 
Maidstone. Bowerbank Col . 
^ Foss. Subs. pi. xxxi. figs. 6, 7. 
* See Proo. Geol. Abboc. vol. x. (1888), p. 298. 
