294 TEILOBITES, THEIR DISTRIBUTION. 



Referring my readers to these valuable commencements 

 of the history of fossil Crustaceans, I proceed to select one 

 very remarkable family, the Trilobites, and to devote to 

 them that detailed consideration, to which they seem pecu- 

 liarly entitled, from their apparently anomolous structure, 

 and from the obscurity in which their history has been in- 

 volved. 



Trilobites. 



The great extent to which Trilobites are distributed over 

 the surface of the globe, and their numerical abundance in 

 the places where they have been discovered, are remarkable 

 features in their history ; they occur at most distant points^ 

 both of the JNorthern and Southern Hemisphere. They have 

 been found all over Northern Europe, and in numerous lo- 

 calities in North America ; and in the Southern Hemisphere 

 they occur in the Andes,* and at the Cape of Good Hope. 



No Trilobites have yet been found in any strata more re- 

 cent than the Carboniferous series ; and no other Crusta- 

 ceans, except three forms which are also Entomostracous, 

 have been noticed in strata coeval w^ith any of those that 



reminded Mr. Broderip of the living Arctic forms of the macrourous deca- 

 pods. 



* I learn from Mr. Pentland that M. D'Orbigiiy has lately found Trilo- 

 bites, accompanied by Strophomena and Producta in tlie Greywacke slate 

 formation of the Eastern Cordillera of the Andes of Bolivia. Fresh-water 

 shells, Melania, Melanopsis, and probable Anodon, occur also in the same 

 rock; a fact which seems analogous to the recent discovery of similar fossils 

 in the Transition rocks of Ireland, Germany, and the United States. The 

 Fresh-water fossils occurred near Potosi, at an elevation of 13,200 feet. 



M. D'Orbigny's specimens also confirm Mr. Pentland's view, as to the 

 analogies between the great Limestone formation of this district, and tlie 

 Carboniferous limestones of England; and as to the great extent also of the 

 Red Marl, and New red sandstone formations on the Continent of South 

 America. 



