172 BRITISH FOSSIL VERTEBRATA. 
PTYCHOLEPIS (continued)— 
gracilis, J. W. Davis, Ann. Mag. Nat. Hist. [5] vol. xiii, 1884, 
Pp. 335, pl. x. 
Loc. L. Lias; Lyme Regis. [Fish ; J. W. Davis Coll.] 
minor, P. M. G. Egerton, Figs. and Descript. Brit. Organic 
Remains, dec. vi (Mem. Geol. Surv., 1852), no. 7, pl. vil; 
J. Morris, Cat. Brit. Foss., 1854, p. 342. 
LOG; .L: Wes Barrow-on-Soar, Leicestershire. [Fishes ; Brit. 
Mus. 
PYCNODUWS, L. Agassiz, Poiss. Foss., vol. i (1833), pl. G, fi 1 
(name and fig. only), and z6z@., vol. ii, pt. ii (1843), p. 183; 
J. J. Heckel, Denkschr. k. k. Akad. Wiss. Wien, math.- 
naturw. Cl., vol. xi, 1856, p. 204. 
PERIODUS, L. Agassiz, Poiss. Foss., vol. ii, pt. ii (1843), p. 201. 
angustus, Agassiz. wv. Coelodus angustus. 
biserialis, Agassiz. wv. Mesodon biserialis. 
bower P. M. G. Egerton, Geol. Mag. [2] vol. iv, 1877, p. 52, 
pL. i, £:.2, 
Loc. London Clay; Sheppey. [R. mandib. dentition; Brit. Mus.] 
bucklandi, Agassiz. v. Mesodon bucklandi. 
cretaceus, Agassiz. wv. Coelodus cretaceus. 
didymus, Agassiz. wv. Mesodon bucklandi. 
discoides, Agassiz. v. Mesodon discoides. 
elongatus, Agassiz. v. Coelodus angustus. 
hugii, L. Agassiz, Poiss. Foss., vol. ii, pt. ii (1843), p. 195, pl. Ixxii a, 
f. 49-54. Erroneously recorded from Stonesfield Slate by 
J. Morris, Cat. Brit. Foss., 1854, p. 342. 
latirostris, Agassiz. v. Mesodon trigonus. 
liassicus, Egerton. wv. Mesodon liassicus. 
mantelli, Agassiz. v. Ccelodus mantelli. 
marginalis, Agassiz. v. Gyrodus cretaceus. 
microdon, Agassiz. v. Ccelodus mantelli. 
minor, L. Agassiz, Poiss. Foss., vol. 1i, pt. ii (1843), p. 200 (name 
only). ? =Gyrodus minor, Agassiz. 
obtusus, Agassiz. v. Mesodon bucklandi. 
ovalis, Agassiz. v. Mesodon bucklandi. 
pachyrhinus, P. M. G. Egerton, Geol. Mag. [2] vol. iv, 1877, 
p54; pl w, £1;72: 
Loc. London Clay; Sheppey. [Vomer ; Brit. Mus.] 
pagoda, Blake. wv. Microdon pagoda. 
parallelus, Dixon. v. Ccelodus parallelus. 
parvus, Agassiz. v. Mesodon rugulosus. 
quincuncialis, Blake. v. Microdon quincuncialis. 
