Yol. 50.] THE SYSTEMATIC POSITION OF THE TRILOBITES. 411 



26. The Systematic Position of the Trilobites. By H. M. Bernard, 

 Esq., M.A., F.L.S., F.Z.S., of the Huxley Research Laboratory, 

 Royal College of Science, Loudon. (Communicated by Dr. 

 Henry Woodward, F.R.S., P.G.S. Read March 7th, 1894.) 



It is now just fifty years since Burmeister x wrote that he " was 

 convinced " that the reasons he afforded would be " deemed suffi- 

 ciently conclusive to satisfy the unprejudiced reader " that " the 

 trilobites were a peculiar family of the Crustacea, nearly allied to 

 the existing phyllopoda, approaching the latter family most nearly 

 in its genus Branchipus, and forming a link connecting the phyllo- 

 poda with the pcecilopoda." Burmeister's reasoning has not, how- 

 ever, been generally considered satisfactory, and his claim that the 

 trilobites are related to the phyllopoda, though recognized as possible, 2 

 appears somewhat to have waned before the claim put forward 

 by others that they are primitive isopods. But this latter relation- 

 ship had already been shown by Burmeister to be highly improb- 

 able, and this judgment is fully endorsed and further enforced 

 by Gerstaecker, whose monumental review of the Crustacea in 

 Bronn's ' Klassen und Ordnungen des Thierreichs ' gives special 

 weight to his opinion. 3 In the abseuce of any certain knowledge as 

 to the character and arrangement of the limbs, Gerstaecker, while 

 recognizing trilobites as Crustacea, declines to adopt any special 

 relationship : that is, he is evidently not convinced by Burmeister's 

 reasoning. And it must indeed be admitted that Burmeister's 

 arguments were, in themselves, far from conclusive, even when 

 correct as far as they went. Since the appearance of the 5th volume 

 of Bronn's ' Klassen und Ordnungen ' in 1879, however, further 

 facts have come to light which completely justify the conclusions of 

 Burmeister, so far, that is, as to the trilobites having been primitive 

 phyllopods. 



My own study of the phyllopod Apus brought me, from the 

 purely zoological standpoint and along an entirely different line of 

 reasoning, to very nearly the same conclusion as Burmeister, or, 

 more strictly, to that adopted by Linnaeus, 4 who decided in favour 

 of classing the trilobites with Monoculus Apus. I endeavoured to 

 show 5 that Apus was the ancestral form of all existing Crustacea 

 (excluding the ostracoda), and, as such, might be expected to throw 

 light on the trilobites. About the same time as my book was 

 published there appeared a long and very valuable paper on the 



1 ' Die Organisation der Trilobiten aus ihrenlebendenVerwandten entwickelt,' 

 Berlin, 1843. See also Engl, transl., edited by T. Bell & Edw. Forbes, Bay Soc. 

 1846. 



2 Lang's ' Text-book of Comparative Anatomy,' English translation, p. 415. 



3 See further the note at the end on the isopod relationship. 



4 A summary of the different views which have from time to time been put 

 forward as to the systematic position of the trilobites is given by Walcott 

 in his short but invaluable paper : ' The Trilobite : New and Old Evidence re- 

 lating to its Organization,' Bull. Mus. Comp. Zool. Harvard, vol. viii. (1880-81). 



5 ' The Apodidse, a Morphological Study,' Nature Series, Macmillan, 1892. 



