CHAPTER VIII 



TUILOB1TA 



AMONG the many interesting groups of fossils found in the 

 Palaeozoic deposits there is none which has attracted more 

 attention than the Trilobites. As early as 1698, Edward 

 Lhwyd, Curator of the Ashmolean Museum in Oxford, recorded 

 in the Philosophical Transactions the discovery of Trilobites in 

 the neighbourhood of Llandeilo in South Wales ; and of one of 

 his specimens he remarked that "it must be the Sceleton of a 

 Hat Fish." In the following year the same writer gave in his 

 Lithophylacii Britannici Iclinoyraphia descriptions and figures of 

 two Trilobites which are evidently examples of the species now 

 known as Ogygia Imchi and Trinvxleus Jimbriatus. 



Although Trilobites differ so much from living Arthropods 

 that it was difficult to determine even whether they belonged to 

 the Crn-taeea or the Arachnida, yet one of the earliest writers, 

 I )r. Cromwell Mortimer, Secretary of the h'oyal Society (1753), 

 recognised their resemblance to A-pus (see pp. 19-36). This view 

 of their affinities was adopted by Linnaeus, and has been supported 

 by many later writers. Another early author, Emanuel Alende/ 

 da Costa, thought that the Trilobites were related ID the Isopods, 

 an opinion which has lieen held hy some lew zoologists of more 

 recent t imes. 



The Trilobites form the only kno\\n Order of the Crustacea 

 which has no living representatives. They are found in the oldest 

 known fossil iferous deposits the Lower ('ambrian or oLi^l/nx 

 beds, where I hey are represented hy I '. -enera heloii-iiiu 1<> the 



families A-liost idae, Taradoxidae, Oleiiidae, and (' < e] ,|ial idae. 



From the variety of forms found and the state of development 

 \\hieh they have reached, it is evident iha! even at thai remote 



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