CRUSTACEA. 645 



and confirmed this opinion of LINNAEUS. He thought that the 

 Trilobites had the closest affinity with Limulus. This opinion was 

 also adopted by some other writers, although to me the affinity with 

 Limulus appears certainly not to be greater, or even not so great, 

 as with Branchipus or Apus. The Trilobites were probably gigan- 

 tic Phyllopoda which peopled the seas of a former world. The re- 

 semblance to the Isopoda appears to me to be rather an analogy 

 than a real affinity. That the Trilobites were possessed of small 

 natatory feet which were soft, and so lost in the petrifying, is very 

 probable 1 . They are all confined to the oldest mountain-strata, in 

 which petrifactions occur, which preceded the coal-formation, and 

 are found especially in the Silurian formation of MURCHISON and 

 other modern geologists. 



Compare on this division amongst others : A. BRONGNIART in the work 

 published by him and DESMAEEST, Hist, natur. des Crustaces fossiles, Paris, 

 1822, 4to. pp. i 65 ; J. W. DALMAN Ueber die Palceaden oder die soge- 

 nannten Trilobiten ; aus dem Schwedischen von FR. ENGELHART. Mib 6 

 Kupfert. Nurnberg 1828, 4to ; H. BURMEISTER Die organisation der Tri- 

 lobiten, aus ihren lebendigen Verwandten entwickelt. Mit 6 Kupfertafeln. 

 Berlin, 1843, 4to ; E. BETRICH Ueber einige bohmische Trilobiten. Berlin, 

 1845, 1846, 2 Stiicke, 4to. m. Kupfert. ; DR EMMRICH Ueber die Trilo- 

 biten in V. LEONHARD u. BRONN, Jahrbuck fur Mineralogie 1845, s - J 8 

 62 ; and especially the admirable work of JOACHIM BARRANDE, with a great 

 number of beautiful plates, Systeme Silurien du Centre de la Bolieme, lere 

 partie ; Eecherches paleontologiques, Vol. I. 1852. Prague et Paris, 4to. 



Some Trilobites did not roll their body up. To these belong the 

 genera : 



Trinudeus MURCHISON (Cryptolithus) , Ogygia BRONGN., Ceraunes 

 GREEN, Arges GOLDF., Brontes GOLDF., Paradoxides BRONGN., 

 \0lenus DALM., BURM., Conocephalus ZENKER, Ellipsocephalus ZEN- 

 IKER, Harpes GOLDF. 



Sp. Olinus Tessini DALM., Entomolithus paradoxus LINN., Mus. Tessinianum 

 Holmise, 1753, fol. Tab. in. fig. T, pp. 98, 99, DALM. 1. 1. Tab. vi. fig. 3. 



Other Trilobites were able to roll themselves up, like Glomeris and 

 some Oniscides, and to bring the shield of the tail to that of the 

 head. They had, as it seems, a harder shell, and commonly a 

 larger tail-shield. To these belong : 



1 It was principally because these feet are not known that LATREILLE arrived at 

 she singular opinion concerning the agreement with Chiton; he says of his own accord, 

 -hat under this point of view he must consider the eyes, which are observed in many 

 ["rilobites, to be tubercles. 



