162 SILURIA. [Chap. VIII. 
in these localities they are accompanied, as in Scotland, and at Ludlow, 
Kington, &c, by the small Lingula cornea. 
Fossils (26). Crustacea and Shells op the uppermost Ludlow Rocks, 
Lanarkshire. 
1. Pterygotus bilobus, Salter ; half the natural size. 2. Portion of a body-joint, to 
show the peculiar sculpture. 3. Swimming-foot, natural size, but with the large basal 
joint incomplete. Fig. 4 shows a pair of these great foliaceous joints, with their inner 
serrate edges (the true mandibles are only indicated by their palpi in dotted lines, fig. 1). 
[In this restoration the body is rather too narrow, and has one segment too few.] 
5. Head (reduced to one-half) of Slimonia acuminata, Salter. 6. Tail of the same 
(reduced to one-fourth). 7. Tail and a few body-joints of Eurypterus lanceolatus. 
8. Lingula cornea, Sow. 9. Platychisma helicites *, Sow. 
In Southern Eussia (Podolia) similar large Crustaceans, analogous to 
Pterygoti, were found in strata lying beneath/ rocks which are known to 
be of Devonian age ; and to one of these Dr. Fischer gave the name of 
Eurypterus tetragonophthalmus. M. d'Eichwaldf has detected several 
species, one of which he figures as Eurypterus remipes J, Dekay, in the Isle 
of QEsel in the Baltic, — i, e. in a limestone which my colleagues and myself 
referred to the highest Silurian stage, and which Professor Schmidt of 
Dorpat has shown, by many of its fossils, to be an exact equivalent of the 
Upper Ludlow rock §. In the North, therefore, as in the South of Eussia 
* Formerly regarded as a Troehus. 
t Bull. Soc. Imp. Nat. Moscou, 1854, vol. xxvii. 
p. 100. 
X Prof. J. Hall, of Albany, refers this specimen 
figured by d'Eichwald to E. tetragonophthalmus. 
§ Murchisonin Journ.Quart. G-eol. Soc.vol. xiii. 
