CHAPTER VII 
TRILOBITA 
AMmoNG 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 
flat Fish.” In the following year the same writer gave in his 
Lithophylactt Britannici Ichnographia descriptions and figures of 
two Trilobites which are evidently examples of the species now 
known as Ogygia buchi and Trinucleus fimbriatus. 
Although Trilobites differ so much from living Arthropods 
that it was difficult to determine even whether they belonged to 
the Crustacea or the Arachnida, yet one of the earliest writers, 
Dr. Cromwell Mortimer, Secretary of the Royal Society (1753), 
recognised their resemblance to Apus (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 Mendez 
da Costa, thought that the Trilobites were related to the Isopods, 
an opinion which has been held by some few zoologists of more 
recent times. 
The Trilobites form the only known Order of the Crustacea 
which has no living representatives. They are found in the oldest 
known fossiliferous deposits—the Lower Cambrian or Olenellus 
beds, where they are represented by 19 genera belonging to the 
families Agnostidae, Paradoxidae, Olenidae, and Conocephalidae. 
From the variety of forms found and the state of development 
which they have reached, it is evident that even at that remote 
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