PRINCIPLES OF ARRANGEMENT. 



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is again divided into Orders, and sometimes Sub-Orders, and 

 each of these into Families. The names of the Orders are 

 usually printed in large type on cards fixed in the Exhibition 

 Cases. The names of the Families are printed on labels 

 mounted on wood and inserted in their places in the series ; 

 they may be recognised by always ending in — idee. The 

 Families again are divided into Genera, each composed of a 

 number of allied Species. The generic names are printed 

 and mounted on wood in similar fashion to the family-names. 



The names on the labels of the separate specimens 

 consist of the name of the genus (e.g. Coiichidium) followed 

 by the trivial name (e.g. hiloGidare), the two together making 

 up the name of the species. This is followed by the name 

 of the author who first described and named the species, 

 e.g. Gonchidmm hUoculare, Linnseus. When the species has 

 been transferred to a genus other tlian that in which it was 

 placed by the original author, then that author's name is 

 placed within brackets or followed by " sp." Thus Briinnich 

 in 1781 described as Trilohus caudatus a trilobite which is 

 now placed in the genus Dalmctnites ; therefore we write 

 Dalmanites caudatus (Bi'iinnich). Since 1839, however, this 

 trilobite has generally been placed in the genus Phacops, and 

 appears in the text-books as Phacops caudatus. In this 

 Guide-book the generic name by which a species is generally 

 known is added to the correct name within square brackets, 

 e.g., Dalmanites \^Phacops\ caudatus (Briinnich). When a 

 genus has been split up into sub-genera, the name of the 

 sub-genus to which a species belongs may be inserted within 

 round brackets between the name of the genus and the trivial 

 name, thus, Ortliis {Dalmanclla) cUgantula. 



Many of the exhibited specimens bear small discs of 

 green or red paper. A green disc indicates that the specimen 

 bearing it either is the original specimen on which the species 

 to which it belongs was based, or has been described and 

 figured in some scientific work, to which a reference is given 

 on the label. Specimens marked with red discs have been 

 merely noticed or briefly described in some published work. 



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