Page:The Habitat of the Eurypterida.djvu/200

192 varied. Traquair, who has made such a careful study of the ichthology of the Old Red Sandstone of Great Britain, has established the following fish zones in the Caithness area (272):

This fish fauna is very different from that to the south of the Grampians in Forfarshire, there being no species in common between the two areas and only two genera, Mesacanthus and Cephalaspis, the latter being represented in Caithness by only a single specimen. From this division no eurypterids have been reported.

In Caithness and in the Orkneys and Shetland isles has been found a phyllopod crustacean of a genus which at present lives in rivers and freshwater lakes and playas, namely, Estheria. T. Rupert Jones has described the species E. murchisonia, which is abundant in a "dark grey, tough, fine-grained, sandy flagstone, slightly micaceous, somewhat varying in tint and hardness. . . . . Great numbers of the valves are spread over large surfaces of the flagstone, sometimes scattered sparsely, sometimes congregated in groups, forming films between the layers of fissile stone" (191, 405). Murchison says of this species: "It occurs in certain localities in such numbers as to form layers an inch or two thick, entirely made up of the thin carapaces" (191, 404).

The Old Red sandstone of Lorne has yielded, besides Pterygotus anglicus remains, two species of chilognathous myriopods, Campecaris forfarensis (Page) and Archidesmus sp. described by Peach (214, 83). These are among the earliest myriopods yet known and suggest that the beds in which they were found were formed on land, for if the myriopods had been transported far they would have been destroyed. Moreover, since they had not hard parts to be preserved, they must have been buried quickly. A playa would be the ideal place for their burial, but I do not know enough about the beds in which they were found to state that they were formed in a playa. Macconochie has