x] SUMMARY OF THE CONTENTS OF THE CATALOGUE. 
group, and are associated with some forms of Gasteropoda, Heteropoda, and Cephalopoda, 
belonging chiefly to the genera Orthoceras, Phragmoceras and Trochoceras. 
The Upper Ludlow mudstones contain representatives of most of the classes previously 
mentioned, the Merostomata affording species of Eurypterus and Pterygotus, as well as the 
interesting genus Hemiaspis; the Lamellibranchiata, among the Mollusca, comprise the largest 
number of specific forms, while the Cephalopoda contain about the same number of species 
(16), as in the preceding group. 
The Ludlow bone-bed and Downton sandstone are represented by few forms, and these 
chiefly belong to the Molluscan classes, for Trilobites have become rare, and Corals and 
Echinoderms are absent, there are however, a few Merostomata (Pterygotus, Hemiaspis), and 
Phyllopoda (Beyrichia, Leperditia). The bone-bed is the marked feature of this group, with its 
numerous fragmentary remains of fish. The Ledbury shales contain but few species, which 
chiefly belong to the Merostomata and Phyllopoda. 

The Catalogue enumerates about 910 named species, but many other forms are noticed, 
together with their localities, to which specific names are not assigned. 
