360 
CROSSOPTERY GII. 
The ethmoidal region is covered with numerous pol} T gonal 
ossifications ; and the forward position of the orbit is well 
shown. The cheek is covered by membrane-bones of which 
the very large posterior element is distinct; and immedi¬ 
ately below these occurs the long slender maxilla, provided 
with a series of small teeth. The form and proportions 
of the operculum and suboperculum are also shown, from 
the inner aspect, on the left side. Of the fins, the anal 
and caudal are best preserved ; and a pair of relatively 
large narrow scales seems to occur in advance both of the 
first dorsal and the anal. Purchased , 1883. 
28870, P. 716. Imperfect smaller fish, in counterpart; Gamrie. 
Purchased , 1854, and Egerton Coll. 
P. 4046. Head and portions of trunk of small fish; Gamrie. 
Parch ased, 1883. 
P. 184-5. Two examples of the head with imperfect trunk, the 
second in counterpart; Orkney. Purchased , 1881. 
An imperfect scale of an indeterminable genus, from a Lower 
Palaeozoic boulder near Meseritz, Silesia, is named Gyroptychius 
posnaniensis, G. Hade, Programm k. Realschule zu Meseritz, 1858, 
p. 16, figs. 6, 7. ffrr. 
ix > p-bs,?/£. /fa- 
Genus TRISTIQS'SOPTEK.TJSj Egerton. 
[Figs. & Descrips. Brit. Organic Remains (Mem. Geol. Surv. 
1861), dec. x. p. 51.] 
Body much depressed anteriorly, with round or ovoid scales, of 
which the exposed portion is ornamented with short, antero- 
posteriorly directed rugae of ganoine. Head-bones more or less 
tuberculated ; teeth round in section. Ossified ring-shaped ver¬ 
tebrae in the abdominal region. Anterior dorsal fin opposed to the 
pel\ ic pair, and the posterior dorsal to the anal; tail heterocercal, 
the caudal fin abruptly truncated posteriorly, having a relatively 
small upper lobe, and the rays at the extremity of the caudal body- 
prolongation extending somewhat beyond the others above and 
below. 
Tristichopterus alatus, Egerton. 
1861. Tristichopterus alatus, Sir P. Egerton, Rep. Brit. Assoc. 1860, 
Trans. Sect. p. /8, and Figs, and Descrips. Brit. Organic Remains 
(Mem. Geol. Surv.), dec. x. p. 51, pis. iv., v. 
