216 
ANTI ARCH A. 
distinguishable, and the tail is well shown. The caudal 
scales are externally tuberculated and deeply overlapping ; 
and the dorsal ridge-scales (/.) beyond the fin are very 
distinct. The impression of one large fulcral scale is 
seen upon the anterior margin of the dorsal fin (d.). 
Purchased , 1883. 
Fterichthys testudinarius, Agassiz. 
[Plate Y. fig. 8; Plate YI. fig. 1.] 
1844. PtericJithys cornutus and P. testudinarius, L. Agassiz, Poiss. Foss, 
vol. ii. pt. i. p. 302 (names only). 
1844. PtericJithys testudinarius, L. Agassiz, Poiss. Foss. Y. G. R. p. 14, 
pl.4y. figs. 1-3. 
1844. PtericJithys cornutus , L. Agassiz, ibid. p. 17, pi. ii. figs. l-o. 
[British Museum.] 
1848. PtericJithys testudinarius, Sir P. Egerton, Quart. Journ. Geol. 
Soc. vol. iv. p. 312. 
1848. PtericJithys cornutus, Sir P. Egerton, ibid. p. 313. 
1855. PtericJithys testudinarius, F. M‘Coy, Brit. Palaeoz, Foss. p. 600. 
1888. PtericJithys cornutus, R. PI. Traquair, Geol. Mag. [3] vol. v. 
p. 509, and Ann. Mag. Nat. Hist. [6] vol. ii. pi. xvii. figs. 1-3. 
Type. Head and trunk ; Edinburgh Museum. 
Inferior surface of carapace narrowly ovate; tail about equal in 
length to the trunk. Pectoral appendages less than two-thirds as 
long as the trunk, not expanded, tapering. 
Form. Sf Loc. Lower Old Red Sandstone : Lethen Bar, Nairn¬ 
shire. 
P. 3202. One of the type specimens of P. cornutus , figured by 
Agassiz, op.cit. pi. wf fig. 2. Enniskillen Coll. 
P. 548, P. 3203. One of the type specimens of P. cornutus , in 
counterpart, figured ibid. fig. 4. 
Egerton Sf Enniskillen Colls. 
P. 549, P. 3201. One of the type specimens of P. cornutus , in 
counterpart, figured ibid. fig. 5. 
Egerton Sf Enniskillen Colls. 
28857 a. Ventral plates of trunk, visceral aspect, with right pec¬ 
toral appendage and remains of tail. Purchased , 1854. 
49180. Trunk, ventral aspect, wanting the tail, with displaced head 
and scattered plates of the carapace. The greater portion 
of the specimen is shown, of the natural size, in PI. Y. 
fig. 8, and the various plates are indicated by the letter¬ 
ing. Purchased , 1878. 
I 
