12 INTRODUCTION. 



rally correct basis which Quenstedt exhibits in this respect. The group of the large-eyed 

 species, furnished with eleven articulations, which was first recognized by the latter, was named 

 Vhacops by Emmerich, and appears as a genus, besides eight others, of which the second 

 {Odontopleura) is also new and well-founded, but cannot be satisfactorily recognized by the very 

 defective illustrative figure. Emmerich has also followed his predecessor in this respect, that 

 he extends the identity of Ilomalonotus and Trimerm, first announced by Murchison (and to 

 which Brenn subsequently — 1840 — also added Blpleuni), to Co/ywrae, considering the group 

 merely as a subdivision of it. He unquestionably, however, goes too far in this respect, 

 especially when he separates from it Bipleum, which of all the three forms is most nearly 

 related to Cali/meue. 



Next to this work there follows a brief but sound and valuable account of the Russian 

 Trilobites by L. v. Buch (1840), containing a correct view of all essential characters, namely, 

 a comparative study of the relative proportions of the head, trunk, and tail, and the relation 

 of the separate parts to the whole. " By proceeding in this manner only can we expect real 

 natural historical classifications, such as rise above the poor purpose of serving as con- 

 venient indices to collections and catalogues." This is perfectly true, but the contemporary 

 works of the Count v. Münster (1840 and 1842) unfortunately do not soar beyond that 

 purpose, for they scarcely furnish a single perfect description of the many new species 

 exhibited, and only indicate obscurely in the illustrative plates the real forms to which they 

 probably belong. 



The paradoxical forms which Goldfuss has published (1841) offer, both in perfection 

 of representation and description, a magnificent contrast to the last work, and cannot be too 

 strongly recommended as a pattern to those who henceforth wish to describe Trilobites from 

 fragmentary specimens. The newest work on this subject, one recently published by 

 Milne Edwards, in the third volume of his ' Histoire Naturelle des Crustaces,' tom iii, 1841, 

 embraces indeed everything connected with the subject, but, on the other hand, is by no 

 means worthy of the name which this distinguished French naturalist has procured for 

 himself by many excellent works. The arrangement of the Trihhites between Isojmks and 

 Phyllopodes, which the author follows, does homage to all the different views hitherto pro- 

 posed on the subject, and therefore does not bring the matter to a decision ; but in this 

 case the truth lies by no means, as it often does in other cases, in the middle. Among the 

 assumed twelve genera, several, as Pleuracanthus, Peltura, and Otarion, are founded on mis- 

 understood fragments, and the same may be said of many species which the author copies 

 from his predecessors without any further investigation. It is to be regretted that so pro- 

 found a zoologist, who may justly be considered by the many as a distinguished authority, 

 has paid so little attention to this part of his otherwise very meritorious volume, and has 

 thus furnished a work which can only be considered valuable as a mere compilation. It 

 certainly has not advanced us one step in our knowledge of the structure of these animals. 



