FOUND ONLY IN TRANSITION SERIES. 295 



contain the remains of Trilobites ;* so that during the long 

 periods that intervened between the deposition of the eariiest 

 fossihferous strata and the termination of the Coal formation,! 

 the Trilobites appear to have been the chief representatives 

 of a class which was largely multiplied into other orders 

 and families, after these earliest forms of marine Crustaceans 

 became extinct. 



The fossil remains of this family have long attracted at- 

 tention, from their strange peculiarities of configuration. 

 M. Brogniart, in his valuable History of Trilobites, 1822, 

 enumerated five genera,J and seventeen species ; other 

 writers (Dalma, Wahlenberg, Dekay, and Green,) have 

 added five more genera, and extended the number of spe- 

 cies to fifty-two ; examples of four of these genera are 

 given in plate 4G. Fossils of this family were long con- 

 founded with Insects, under the name of Entomolithus para- 

 doxus; after many disputes respecting their true nature, 

 their place has now been fixed in a separate section of the 

 class Crustaceans, and although the entire family appears 

 to have been annihilated at so early a period as the termi- 

 nation of the Carboniferous strata, they nevertheless present 



* In Scotland two genera of Entomostracous Crustaceans, the Eurypterus, 

 and Cypris, occur in the Fresh-water limestone beneath the Mid Lothian 

 Coal Field; the Eurypterus at Kirkton, near Bathgate, and the Cypris at 

 Burdiehouse, near Edinburgh. (Trans. Royal Soc. Edin. vol. xiii.) The 

 third Genus, Limulus, has but recently been recognised in the Coal Forma- 

 tion, and will be described presently. The Entomostracans appear to have 

 been the only representatives of the Class Crustaceans until after the deposi- 

 tion of the Carboniferous strata, 



T Trilobites of a new species have lately been found in Ironstone from the 

 centre of the coal measures in Coalbrook-dalc. Lond. and Edin. Phil. Mag, 

 vol. 4. 1834, p. 376. 



X The names of these Genera are Calymene, Asaphus, Ogyges, Para- 

 doxus, and Agnostus. Some of these terms are devised expressly to denote 

 the obscure nature of the bodies to which they are attached; e, g. Asaphus, 

 from a.<r!t<p>i(, obscure; Calymene, from ■xix.xw/x/unvii, concealed; •^xfAS't^Hr 

 wonderful; aj.i'aa-To;, unknown. 



