Table-eases 
B, C. 
Table-cases 
D, E. 
58 GUIDE TO THE FOSSIL REPTILES, AMPHIBIANS, FISHES. 
specially characteristic of the Lower Devonian both in Europe 
and North America. The unique collection of Cephalaspis 
murchisoni (Fig. 53) from the Lower Old Bed Sandstone 
Passage Beds of Herefordshire, and fine specimens of other 
species from the Lower Old Pied Sandstone of Scotland, 
exhibit nearly all the principal characters of the family 
(Table-cases B, C). At the back of the head region there is 
a pair of flippers, which seem to have assisted the expulsion 
Fig. 53.—Restoration of Cejohalaspis murchisoni, left side-view, from the 
Lower Old Red Sandstone Passage Beds of Herefordshire; about one- 
half nat. size. (After A. S. Woodward. Table-case B.) 
of water from the gill-cavities. The scales on the sides of the 
trunk are deep and narrow. There is a small dorsal fin, and 
the tail is heterocercal (see p. 61). The Tremataspidse com¬ 
prise Trematasjois from the Upper Silurian of the Isle of 
Oesel (Baltic Sea) and Didymasjois from the Lower Old Bed 
Sandstone Passage Beds (Downtonian) of Herefordshire. 
Sub-order 4.—Antiarchi. 
These are the highest Ostracoderms, and are exclusively 
Devonian both in Europe and North America. The head and 
the anterior part of the trunk are covered with symmetrically- 
arranged overlapping plates, of which the lower layers 
contain bone-cells. The eyes are close together on the top of 
the head, which is movable on the trunk. A pair of toothed 
jaws of an unusual kind is fixed in front of the mouth. A 
pair of paddle-like appendages, each encased in plates and 
divided by one movable cross-joint, is articulated with the 
anterior angle of the body. The tail is heterocercal, and 
there is at least one small dorsal fin. The earliest known genus, 
Pterichthys (Fig. 54), is represented by an unique collection of 
specimens from the Middle Old Bed Sandstone of Scotland 
in Table-case D; and with these there are two paper models 
made by the original discoverer, Hugh Miller. The tail of 
Pterichthys is scaly, but that of the Upper Devonian genera 
