INTRODUCTION. 



Angelin's Palseoutologia Scandinavica is of great importance for the Silurian 

 geologist, but at the same time very little handy because of the want of an index. 

 Owing to the lack of a uniform plan and disposition ^ of this work, an index to it 

 is so indispensable that everybody, who has occupied himself somewhat closer with 

 the trilobites of Sweden, must have compiled one for himself. 



It is in the hope of being able in some measure to facilitate the use of 

 Angelin's work that I have composed the present index. Of course a complete 

 revision of Palœontologia Scandinavica had been most desirable, but this would 

 have been a much too long and exacting task, which is also, no doubt, best carried 

 out in connection with a thorough revision of our trilobite fauna in general. 



In expectation of such a work I have, however, thought convenient to some 

 degree to make up for its lacking by here, under the heading »Notes», bringing 

 together the most important of the alterations, which Angelin's denominations 

 have suffered by the publications of different authors, always referring to the works 

 in which these alterations have been exposed. 



As Barkande has already pointed out, Angelin's diagnoses, in the same man- 

 ner as those of Linn^us, are always short, not to say incomplete, and his figures 

 very often rather badly drawn. It has therefore seemed opportune in the »notes», 

 wherever it has been possible, also to refer to later works, containing a more 

 detailed description or completer and more natural figures. 



^ With regard to the arrangement of Palaeontologia Scandinavica the following is to be ob- 

 served. The description always follows the numbers of the plates and figures, which form special 

 successive headings, whether the description of the species is given immediately after or other- 

 where, which arrangement may well be considered to sufficiently account for the otherwise impar- 

 donable leaving out of special explanations annexed to the plates in the original edition. The 

 order in which the different genera are given does not seem to be determined by any general 

 leading principle. True, Angelin has in the second fasc. of his work, which fasc. appeared in 

 1854, after the example of Baeeande's first part of »Systéme silurien du centre de la Bohême», 

 edited in 1852, brought together the genera to families, but for the rest one cannot find that any 

 special systematical or stratigraphical order has been observed. 



As for the terminology adopted by Angelin, we may here content ourselves to mention 

 that, where we should use the word hypostoma, he always uses the word episioma. 



