PIS CES: 169 
. PTYCHACANTHUS, L. Agassiz, Poiss. Foss., vol. iii (1837), 
' . 22. = Tristychius and undetermined genera. 
dubius, L. Agassiz, Poiss. Foss., vol. iii (1843), p. 176, and Poiss. 
Foss. V. G. R. (1844), p. 118, pl. xxxiii, f. 22,23; J. Morris, 
Cat. Brit. Foss., 1854, p. 341. [Undetermined ichthyolite.] 
Loc. L. Old Red Sandst.; Abergavenny. [Spine ; o/z# Mur- 
chison Coll.] 
subleevis, Agassiz. wv. Tristychius arcuatus. 
? sp., L. Agassiz, in Murchison’s Silur. Syst. (1839), p. 597, pl. i, 
f. 9, 10; J. Morris, Cat. Brit. Foss., 1854, p. 341. 
Loc. L. Old Red Sandst.; Abergavenny and Herefordshire. 
[Spine ; 0/7 Murchison Coll.] 
PTYCHOCEPHALUS, L. Agassiz, Poiss. Foss., vol. v, pt. ii 
(1843), p. 139 (name only), and Rep. Brit. Assoc. 1844 
(1845), p. 307 (name only). 
radiatus, L. Agassiz, zbzd@. (1843), p. 139 (name only), and zéz@,, 
1844, p. 307 (name only). 
Loc. London Clay ; Sheppey. [Imperfect head; Brit. Mus.] T. 
PTYCHODUS, L. Agassiz, Poiss. Foss., Feuill., p. 54 (1835), and 
vol. iii (1839), p. 150; A. S. Woodward, Cat. Foss. Fishes 
B. M., pt. i, 1889, p. 132. 
AULODUS, F. Dixon, Geol. Sussex, 1850, p. 366. 
acutus, L. Agassiz, Poiss. Foss., vol. ili (1843), p. 177 (name only) : 
recorded from Gault of Folkestone by J. Morris, Cat. Brit. 
Foss., 1854, p. 341. 
altior, Agassiz. v. Ptychodus mammillaris and P. rugosus. 
arcuatus, Agassiz. v. Protosphyrzena (fins of). 
articulatus, Agassiz. wv. Protosphyrzena (fins of). 
concentricus, named variety of P. poly gyrus (L. Agassiz, Poiss. 
Foss., vol. ili (1839), p. 156). 
decurrens, L. Agassiz, Poiss. Foss., Feuill., p. 54 (1835), and 
vol. iii (1839), p. 154, pl. xxv 4, f. 1, 2, 4, 6-8 (mon f. 3,5); R. 
Owen, Odontogt. (1840), descr. to pls. xviii, xix; F. Dixon, 
Geo), Sussex, 1650, p. 362, pl. sxx, £7, 8, pl. xxxi, f. 1, 
pl. xxxii, f. 5 ; J. Morris, Cat. Brit. Foss., 1854, p. 341; A. S. 
Woodward, Quart. Journ. Geol. Soc., vol. xlili, 1887, p. 123, 
| pl. x, f. 1-10, 13, and Cat. Foss. Fishes B. M., pt. i, 1889, 
p- 138. [See also P. mammillaris.) 
‘Palate of Unknown Fish,’ J. Parkinson, Organic Remains, 
| vol. iii, 1811, p. 262, pl. xviii, f. 12. 
Ptychodus depressus, F. Dixon, Geol. Sussex, 1850, p. 363, 
pl ‘axxi, #93]. Morris, Cat. Brit. Foss., 1854, p. 341. 
[Tooth ; Brit. Mus. ] 
| Loc. U. and L. Chalk ; Sussex, Kent, Surrey, Cambridgeshire, 
and Norfolk. [Teeth ; Brit. Mus. (Zars).] 
depressus, Dixon. wv. Ptychodus decurrens. 
| 
