P-ECILOPODA. 155 



on the branchiae of the Lobster, and before their thoracic lobes 

 have acquired their ordinary development, they can swim; that 

 development, as is the case with the body of the Ixodes, may 

 be the result of superabundant nutrition. 



TRILOBITES. 



According toBrongniartand various other naturalists, it is 

 in the vicinity of the Limuli and other Entomostraca with 

 numerous feet, that we should place these singular fossil ani- 

 mals, originally confounded under the common name of Ento- 

 inolithus paradoxus^ and now designated by that of Trilobites, 

 of which an excellent monograph, enriched with good litho- 

 graphic figures, has been published by that gentleman(l). By 

 this hypothesis we have to admit as a positive or at least 

 highly probable fact, the existence of locomotive organs, al- 

 though, notwithstanding the most careful investigation, no 

 vestige of them has been discovered (2). Presuming, on the 

 contrary, that these animals were deprived of them, I thought 

 that their natural position was in the neighbourhood of the 

 Chitones, or rather that they constituted the original stock of 

 the Articulata, being connected on the one hand with these 

 latter Mollusca, and on the other with those first mentioned, 

 and even with the Glomeres(3), to which some Trilobites, 



(1) M. Eudes Deslongchamps, professor of the University of Caen, Count Ra- 

 soumowski, M. Dalman and other savans have since published new observations 

 on these fossils. M. Victor Audouin, zealously advocating the opinion of Brong- 

 niart, has contested that published by me, in which I approximate them to Chiton. 

 The great difficulty was to prove the existence of feet, and this he has not done. 

 The application of his theory of the thorax of Insects to the Trilobites, appears to 

 me so much the more doubtful, as, according to my view of the matter, the first 

 annuli of the abdomen of Insects alone represent the thorax of the Crustacea De- 

 capoda. 



(2) M. Parkinson (Outlines of Oryctology) thinks he has perceived them, and 

 suspeots that they are unguiculated. See also the Entomostradte granukuz 

 Brongn., Trilob., Ill, 6, Ann. des So. Nat. tome XV. 



(3) First edition of the Regne Animal, tome III, p. 150, 151. There is no 

 Branchiopoda known which can contract itself into the form of a ball. This cha- 

 racter is peculiar to Typhis, Spharoma, Tylos, and Armadillo among the Crus- 

 tacea; and among the class of apterous Insects to Glomens, a genus which is at the 



