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among living animals to the external form of Trilobites is that 

 afforded by the genus Serolis in the class Crustacea. The genus 

 Serolis inhabits the Straits of Magellan and the coast of Pata- 

 gonia. The beach is often seen covered with them dead ; they 

 are found alive only by dredging in deep water. This region is 

 but little known^ but the above approximation is sufficient for 

 our present purpose. All the deposits found within this region 

 are comparatively recent, containing organic remains of those 

 only which inhabit the bordering sea. 



2. South temperate deposits, or Carboniferous groups. 



The forms of life buried in this system of strata are exceed- 

 ingly numerous and varied, and generally in an excellent state 

 of preservation, allowing of a most strict comparison with exist- 

 ing types. They consist of many races of plants, abundance of 

 Zoophyta, with multitudes of Mollusca, Crustacea and Fishes. 

 The plants are in some respects very similar to existing races, as 

 the large group of ferns generally, the Equiseta, Lycopodiaceae, 

 Araucaria, Cycadeae, Coniferae, &c. The remains of these plants are 

 often abundant in coal-seams. The coal plants of North America 

 are for the most part identical with those of Europe, and all belong 

 to the same genera. Specimens from Greenland are referrible to 

 ferns, analogous to those of our European coal mines. The fossil 

 plants brought from Melville Island warrant similar < onclusions. 

 The coal formation of Bogota, which is situated within 4° north 

 of the equator, at an elevation of about 8000 feet above the level 

 of the sea, contains the same kind of plants —arborescent ferns, 

 and Lycopodiaceae of the same species as those now growing in 

 the southern hemisphere. The living representatives of the above 

 are found in New Holland, New Zealand, Brazils, Chili, and va- 

 rious islands within the south temperate zone. Not a single 

 species of Cycadeae is known to grow in the north temperate 

 region ; their principal localities are equinoctial America, and 

 southward of that part, the Cape of Good Hope, Madagascar, 

 India, the Molucca Islands and New Holland. 



The enlarged size of the arborescent ferns depend not only on 

 a warm temperature, but also on a shady and moist place. 

 Within the tropics they are found at an elevation of about 4000 

 feet above the sea, from twenty to thirty feet high, flourishing 



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