PRINCIPLES OF ARRANGEMENT. 
3 
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 — idea. 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. ConcMdium) followed 
by the trivial name (e.g. hiloculare), 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. ConcMdium hiloculare, Linnaeus, When the species has 
been transfeiTcd to a genus other than that in which it was 
placed by the original author, then that author’s name is 
placed within brackets or followed by “ sp.” Tims Briinnich 
in 1781 described as Trilohiis caudatns a trilobite which is 
now placed in the genus Dalmanites ; therefore we write 
Dalmanites caudatus (Briinnich). Since 1839, however, this 
trilobite has generally been placed in the genus Fhacops, 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 within square brackets after the correct name 
e.g., Dalmanites \Phacop>s~\ 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, Orthis {Dalmanclla) elegantula. 
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 (a so-called type-specimen), 
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 briefiy described 
in some published work. 
