SELICIIII. 
i;5s 
Ptychodus oweni, Dixon. 
1850. P/ychoduH owani, F. Di.xon, Foss. Suss. p. 364, pi. xxxi. 
Type. Detaclied tooth ; British Museum. 
Iceth with rounded, moderately elevated crowns, ornamented 
with widely separated ridges, whieh rarely extend directly from side 
to side, but arc disposed in an irregular manner ; the marginal 
fine!}' marked area is insignificant. 
Ibis species is very imperfectly known and appears to be rare. 
Form. Lor. Senonian : S.E. England. 
39125, 39125 a. Type specimen and four associated teeth ; Upp®'" 
Chalk, Snodland, Kent. One of the teeth, shown in I’h 
fig. 8, evidently represents the lower median row : a few 
of the transverse ridges upon the crown are continuous, 
regular, and parallel in the middle, but those placed pos- 
teriorly are very irregular and discontinuous. 
Bowerhanh Coll. 
39700. Abraded and worn tooth, supposed lower median ; Kent. 
Purchased, 1866. 
P. 2688. Similar tooth ; Sussex. Kmiiskillen Coll. 
28342. Typical tooth ; Lewes, Sussex. Di j'on Coll. 
Ptychodus decurrens, Agassiz. 
1762. Dem pUck Osfracionk, F. E. Bruckmann, Acta Phys. Med 
vol. ix. p. 116, pi. V. fig. 4. 
1811. Palate of Unknown Fish, J. Parkinson, Organic Kemain.s vol. iii- 
pi. xviii. fig. 12. ® 
1839. Ptychxhm deeurrms, L. Agassiz, Poiss. Foss. vol. iii. p. 154, 
pi. XXV. b. figs. 1, 2, 4, 6-8 {non figs. 3, S). 
1840-45. Ptychodus decurrens, R. Owen, Odontography, vol.'ii. pD. xviii., 
Ptychodus deewrens, F. Dixon, Foss. Suss. p. 362, pi. xxx. 
figs. 7, 8, pi. xxxi. fig. 1, pi. xxxii. fig. .5. 
18M. Ptychodus depressus, F. Dixon, op. cit. p. 303, pi. xxxi. fig. 0. 
18.52. Ptychodus decurrens, P. Gervais, Zool. et I’aL Franc, pi. Ixxviii. 
fig. 5. 
18.52. nychodus decurrens, V. KiprijanofF, Bull. Soc. Imp. Nat. Moscou, 
P- P*- *fi‘- 4', 5. 
186^. Ptychodus decurrens, F. A. Quenstedt, llandb. Petrefakt. p. 181, 
pi. xiii. fig. 59. 
P. 
The original of this figure is a doubtful tooth subsequently assigned to 
owem (V. Kiprijanotr, toe. cit. 1881, pt. jj, p, 2). 
