CRUSTACEA. 645 
and confirmed this opinion of Linnazus. 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 Zsopoda appears to me to be rather an analogy 
than a real affinity. That the Zrilobites were possessed of small 
natatory feet which were soft, and so lost in the petrifying, is very 
probable’. 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 Murcuison and 
other modern geologists. 
Compare on this division amongst others: A. BRONGNIART in the work 
published by him and Drsmarest, Hist. natur. des Crustacés fossiles, Paris, 
1822, 4to. pp. 1—65 ;—J. W. Datman Ueber die Palceaden oder die soge- 
nannten Trilobiten ; aus dem Schwedischen von FR. ENGELHART. Mit 6 
Kupfert. Nurnberg 1828, 4to ;—H. Burmeister Die organisation der Tri- 
lobiten, aus thren lebendigen Verwandten entwickelt. Mit 6 Kupfertafeln. 
Berlin, 1843, 4to ;—E. Bryricu Ueber einige bihmische Trilobiten. Berlin, 
1845, 1846, 2 Stiicke, 4to. m. Kupfert.;—Dr Emmricu Veber die Trilo- 
biten in V. LEONHARD u. Bronn, Jahrbuch fiir Mineralogie 1845, s. 18— 
62; and especially the admirable work of JoAcHIM BARRANDE, with a great 
number of beautiful plates, Systéme Stlurien du Centre de la Bohéme, tere 
partie; Recherches paléontologiques, Vol. 1. 1852. Prague et Paris, 4to. 
Some Z'rilobites did not roll their body up. To these belong the 
genera : 
Trinucleus MuRcHISON (Cryptolithus), Oqgygia BRONGN., Ceraunes 
GREEN, Arges GoLpF., Brontes GoLpF., Paradoxides Bronen., 
Olenus Daum., BurM., Conocephalus ZENKER, Lllipsocephalus ZEN- 
KER, Harpes GOLDF. 
Sp. Olinus Tessint DauM., Entomolithus paradoxus Linn., Mus. Tessinianum 
Holmie, 1753, fol. Tab. 111. fig. 1, pp. 98, 99, Daum. 1. 1. Tab. vi. fig. 3. 
Other 7'rilobites 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 Tt was principally because these feet are not known that LATREILLE arrived at 
the singular opinion concerning the agreement with Chiton ; he says of his own accord, 
that under this point of view he must consider the eyes, which are observed in many 
Trilobites, to be tubercles, 
