TRILOBITES, THEIR DISTRIBUTION. 
380 
ttieiicements of the history of fossil Crustaceans, 
I proceed to select one very remarkable family, 
the Trilohites, and to devote to them that detailed 
Consideration, to which they seem peculiarly en- 
htled, from their apparently anomalous struc- 
ture, and from the obscurity in which their history 
lias been involved. 
Trilobiles. 
The great extent to which Trilohites are dis- 
tributed over the surface of the globe, and their 
Numerical abundance in the places where they 
have been discovered, are remarkable features 
ui their history; they occur at most distant 
points, both of the Northern and Southern Hemi- 
sphere. They have been found all over Northern 
hiUrope, and in numerous localities in North 
■America; in the Southern Hemisphere they occur 
la the Andes,* and at the Cape of Good Hope. 
®i'ce at this early period of a crustaeean approaching to Pali- 
‘''Bus, and as large as our common Sea Crawfish. 
Two other specimens exhibit the breathing organs of anotlier 
'klicate Crustacean, with the tips of the four larger and four 
“^oialler branchise preserved, and pointing towards the region of 
ft, showing that these fossil Crustaceans belonged to the 
division of the Macroura, They reminded Mr. Broderip 
the living Arctic forms of the inacrourous decapods. 
* 1 learn from Mr. Pentland that M. D’Orbigny has lately 
fund Trilohites accompanied by Strophomena and Producta in 
U'e Greywacke slate formation of the Eastern Cordillera of the 
tides of Bolivia. Fresh water shells, Melania, Melanopsis, and 
Ptobably Atiodon, occur also in the same rock ; a fact which 
