194 BULLETIN OF THE 



of secondary importance, and that, beyond a doubt, they belong to this 

 group of the animal kingdom. 



2d. That they exhibit the greatest analogies with the Jsopodes, 

 particularly with Cymothoa and Ligia. 



3d. That the want of feet seems to be a necessary characteristic of 

 their skeleton formation, although this point still remains proble- 

 matical. 



4th. That these feet, if they existed at all, were most probably 

 connected wnth the branchial apparatus. 



These conclusions are introduced here as they evidently had much 

 to do with the direction of future research, especially the 1st and 4th. 



Wahlenberg followed closely in the steps of Linnaeus. He believed 

 that the Trilobite was most nearly allied to Limulus, and was inclined 

 to transfer this similarity to the structure of the feet. The feet in the 

 Trilobite, being smaller, were not observed in the fossils. He noted 

 the corresponding solidity of the head-plate of the Trilobite and Limu- 

 lus, and adds, that, from the various considerations given, we may 

 assume that it, the Limulus, is now amongst living crustaceans the 

 last remaining member of the voracious family which was formerly 

 represented by the Trilobites. 



1822. " Brongniart," Burmeister observes, "expresses the correct 

 view with reference to the zoological relations, namely, that the Trilo- 

 bites are most nearly related to the Branchioj^odes among the Crus- 

 tacea, and that the want of visible feet, as well as of visible antennae, 

 accords very well with this." 



1826. Dalman came to nearly the same conclusions as Wahlenberg, 

 seeing a connection of affinity between the Trilobites and Limxdus, 

 Aj)us and Branchipus, and one of analogy only between them and 

 Sjihoproma, Cymothoa, and Idotea ; or, generally, of affinity between 

 the Palceades (Trilobites) and Monocidi, and of analogy between the 

 Palmades (Trilobites) and Onisci. 



1836. Dr. Buckland considered Serolis, Limulus, and Branchipus 

 as the three living genera of Crustacea to which the Trilobites were 

 most nearly related. 



1843. J. E. Portlock, " Geology of Londonderry," says : " We 

 may assume a group, formod of Asaphus, Isotelus, Jlcenus, Nileus, 

 Bum,astis, etc., would constitute a true connecting link in the chain 

 of organization between these obscure fossil crustaceans and the recent 

 genera Limulus and Apus.^^ 



1843. The work of Burmeister, " Organization of Trilobites," marks 



