Central Bohemia, by Joachim Barrande.^ 315 



gans either did not exist, or were of such a soft and perish- 

 able nature as to leave no recognisable impression on the 

 rock. Adouin and Burmeister both came to this conclusion, 

 from considerations drawn from other features in their 

 organization, and none of the instances of the supposed 

 discovery of feet have borne the test of strict investigation. 

 It is different with the intestinal canal of the Trinucleus, 

 first observed by Professor Beyrich, which the author has 

 also discovered in many specimens of the same species. 

 These were found in the quartzites of the Drabow moun- 

 tains, and the intestine which runs down the interior of the 

 median lobe or axis, from the glabella to the posterior mar- 

 gin of the pygidium, is either empty or full of a very fine 

 clay. The chemical nature of this substance would be inter- 

 esting, as giving, perhaps, some indications of the food of 

 these crustaceans. 



Our limits compel us to pass, without further notice, the 

 very important section on the nature and ornaments of the 

 shell or test of the trilobites, some portions of which furnish 

 valuable materials not only to the geologist, but to the zoolo- 

 gist. The account of the metamorphoses which many of 

 the trilobites are now shewn to undergo, is also well worthy 

 of the study of the zoologist, as illustrating many particulars 

 in this remarkable peculiarity of the articulata. In several 

 species the author has followed the successive changes from 

 the time when the young trilobite escapes from the egg* 

 till it attained its full dimensions. In some this was not 

 possible, as the animal in its early stages seems, like some 

 recent crustaceans, not to have possessed a shell, and thus 

 to have left no record of its first forms. The Sao hirsuta 

 and Dalmanites socialis furnish the most complete series of 

 changes, the young animal being represented merely by 

 the head divided into three lobes, whilst the thorax is 

 wanting or rudimentary, and no trace seen of the tail. In 

 a second group, as Trinucleus ornatus and the Agnosti, 

 even in the first period the head and pygidium are distinctly 

 seen, but incomplete, and there is no trace of the thorax, of 



* The eggs themselves are figured in Plate 27, fig. 1-3. 



