290 H. Woodward — On the Structure of Trilohites. 



have possessed that firm basis, which all solid organs of locomo- 

 tion require, in order that they may be properly available. That 

 this abdominal surface also must have been of a membranous nature, 

 seems quite clear, since it has in no instance been preserved in a 

 fossil state, whilst the hard, horny, perhaps calcareous, dorsal surface 

 is invariably retained." 



Prof. Burmeister refers them therefore to the Entomostraca, from 

 the numerous (not definite) number of the segments of the body, 

 and is disposed to place them among the Phyllopoda. Prof. M'Leay 

 gives them a higher position, intermediate between the Isopods and 

 Phyllopods, he thinks " they probably adhere in masses, as chitons 

 do ; and as the mouth is like that of Apus, they were probably 

 carnivorous as in that genus." (Silurian System.) 



Although M. Barrande, in his magnificent work on the Trilobites 

 of the Silurian System of Bohemia, has illustrated the development 

 of some thirty species, he has not observed appendages in any of the 

 250 species he has so splendidly pourtrayed.^ 



MM. Milne-Edwards, Dana, and most other Carcinologists have 

 accepted Prof. Burmeister's views as to the Phyllopodous affinities 

 of the Trilobita. 



After reviewing the observations of the va,rious writers who had 

 preceded him, Mr. Salter observes (in his Monograph of British 

 Trilobites, part i., 1864, p. 9, Pal. Soc), "We are compelled to con- 

 clude that Trilobites had not even membranaceous feet, and that the 

 ventral surface was destitute of appendages. It is of course difficult 

 to prove this, and almost all naturalists are disposed to allow them 

 soft gills attached to the under side." " I do not see," adds Mr. 

 Salter, " that the Trilobites had any need of appendages further 

 than what might be necessary as breathing organs." " There is 

 some reason to believe that, like its predecessor, the Annelide, the 

 habit of the Trilobite was to gorge itself with the carbonaceous mud, 

 and extract from it the nutritive portions." " The only hard portion 

 of the under side is the immovable upper lip or labrum ; and this 

 may have been the instrument by which the food was scraped 

 together." 



In referring to them in various papers which I have published,^ I 

 have stated that as "no traces of antennse or limbs had yet been 

 detected, it seemed certain that the other appendages of the animal 

 were wholly composed of soft and delicate tissue, too soft to have 

 been preserved in the fossil state." 



The first announcement indicative of any change in these opinions 

 was made before the Geological Society of London on May 11th, 

 1870, by E. Billings, Esq., F.Gr.S., Palaeontologist to the Geological 

 Survey of Canada, Montreal. 



The author described a specimen of AsapJius platycepJialus in which 



1 M. Barrande refers to what lie believes to be the cast of the straight intestinal 

 canal in a species of Trinucleus. 



2 "Intellectual Observer," vol. viii., 1865, p. 324. "Descriptive Catalogue to 

 Chart of Fossil Crustacea," p. 14, by J. W. Salter and H. Woodward, 1865. Eeports 

 on the Structure and Classification of the Fossil Crustacea, British Association, 1864-70. 



