298 
SILUEIA. 
[Chap. XII. 
Fossils (77). 
A Limuloid Crustacean of the 
Carboniferous Period. 
bony palates of other genera — Psammodus, Cochliodus, Helodus, &c, together 
with the fin-defences above mentioned, are the only parts preserved ; but these 
are sufficient to show that they were very numerous as individuals, and con- 
sisted of many genera. These must be studied in the great work of Agassiz, or 
in the subsequent publications of Sir Philip Egerton and other authors *. 
In the coal-field of Kilkenny in Ireland a very important discovery has re- 
cently been made of several remains of Reptiles, which will be treated ofwhen 
the organic remains are described (p. 303). 
It is in the purely marine or central lime- 
stones of the Carboniferous epoch that the 
geologist takes his final leave of Trilobites. 
Abounding in the Silurian era, these Crusta- 
ceans have dwindled to a comparatively small 
number in the Devonian, whilst in the Lower 
Carboniferous, the three genera Phillipsia, Grif- 
fithides, and Brachymetopus mark the last 
appearance of any individuals of this family in 
the ascending scale of primeval deposits. On 
the other hand, it is among the upper coal 
strata, where Trilobites become extinct, that 
we see the first representatives of the Limulus, 
the type of a suborder of Crustaceans which has 
existed from that early period to the present 
day with but comparatively little change in 
structure. 
One example of these old Limuloid animals is here given ; it is a rarer 
species than Belinurus trilobitoides (Limulus, Bucklandf)- Prestwichia an- 
thrax (Limulus, Prestwich) is another rare form also from Coalbrook Dale }. 
Not only are there Crustacea of the tribe to which the King-crab belongs in 
the coal, but other Crustacea of a higher order ; for, both in the South Stafford- 
shire coal-field and in those of Glasgow and Manchester, a peculiar form, pro- 
bably of the Schizopod group, occurs, which Professor Huxley has described 
under the name of Pygocephalus Cooperi j and to this group, too, most probably 
belongs the carapace from Coalbrook Dale figured by Sir Charles Lyell, in his 
Manual of Geol. 5th edit. p. 388, which was first referred to Apus by Milne- 
Edwards, and more lately regarded as a Crustacean of the Shrimp family by Mr. 
Salter. Nor must we omit to mention the large Eurypteri found in the Glasgow 
coal-field, and first described by Hibbert in the Trans. Roy. Soc. Edinb. vol. xiii. 
These, with some others, an Amphipod ? (Gampsonyx or Uronectes fimbriatus, 
Jordan) from Germany, and numerous Bivalved Entomostraca, chiefly of small 
size, show the fauna of the coal to have been rich in Crustacean forms. Still 
higher Articulata, the Scorpion and Spider, also appear for the first time in the 
Coal-measures (Bohemia and Silesia). 
Here also we last meet with any large Orthocerata. Those predaceous mollusks 
of the ancient seas have now begun to diminish rapidly, and with them most of 
the genera of Cephalopods which have a simple form of air-chamber, their office 
being taken, in the Triassic and later Secondary strata, by other groups of Ce- 
Prestwichia rotundata (Limulus, 
Prestwich). From the Coal-mea- 
lts sures of Coalbrook Dale. 
* See ' Palichthyologic Notes,' by Sir Philip de 
M. Grey Egerton, Bart., M. P., in several volumes 
of the Quart. Journ. Geol. Soc. See also the De- 
cades belonging to the Memoirs of the Geological 
Survey of England, in which that distinguished 
naturalist has published admirable descriptions of 
many fossil Fishes. The collections of Ichthyo- 
lites made by Sir P. Egerton and his associate, the 
Earl of Enmskillen, are, it is believed, unrivalled. 
t See the Bridgewater Treatise, pi. 46". fig. 3, — 
that very remarkable work of my eminent friend 
the late Dean of Westminster. 
I Trans. Geol. Soc. vol. v. pi. 41. f. 1, 4. 
