THE, UPPER SILURIAN) PERIOD. 125 
narrow, sword-shaped spine. Fragments of the skeleton are 
easily recognised by the peculiar scale-like markings with 
which the surface is adorned, and 
which look not at all unlike the 
scales of a fish. ‘The most fam- 
ous locality for these great Crus- 
taceans 1s Lesmahagow, in Lan- 
arkshire, where many different 
species have been found. ‘The 
true King-crabs (Zzz/z) of exist- 
ing seas also appear to have been 
represented by at least one form 
(Weolimulus) in the Upper Silu- 
rian. 
Coming to the A/ollusca, we 
note the occurrence of the same 
great groups as in the Lower 
Silurian. Amongst the Sea- 
mosses (/olyzoa), we have the 
ancient Lace-corals (/enestella 
and fefepora), with the nearly- 
allied Glauconome, and species of 
Ptilodiciya (fig. 66) ; whilst many 
forms often referred here may 
probably have to be transferred 
to the Corals, just as some so- 
called Corals will ultimately be 
Fig. 
viewed from the under side, reduced 
65.— Pterygotus Anglicus, 
in size, and restored. cc, The feelers 
(antennz), terminating in nipping- 
removed to the present group. 
The Brachiopods continued 
to flourish during the Upper 
Silurian period in immense num- 
claws ; 0 0, Eyes ; 7 #, Three pairs of 
jointed limbs, with pointed extremi- 
ties ; 72 2, Swimming-paddles, the bases 
of which are spiny and act as jaws. 
Upper Silurian, Lanarkshire. (After 
; Henry Woodward.) 
bers and under a greatly in- 
creased variety of forms. The three prominent Lower 
Silurian genera Orthis, Strophomena, and Leftena are still 
well represented, though they have lost their former pre- 
eminence. Amongst the numerous types which have now 
come upon the scene for the first time, or which have now a 
special development, are Spiérifera and Pentamerus. In the 
first of these (fig. 69, 4, c), one of the valves of the shell (the 
dorsal) is furnished in its interior with a pair of great calca- 
reous spires, which served for the support of the long and 
fringed fleshy processes or “ arms” which were attached to the 
sides of the mouth.* In the genus Pentamerus (fig. 70) the 
* In all the Lamp-shells the mouth is provided with two long fleshy 
organs, which carry delicate filaments on their sides, and which are 
