29 
The Trilobites are amongst the commonest and most Case 39. 
interesting of the Australian fossils. In the Silurian 
Table-case are Trinucleus (with head-spine) ; 
Gordius (formerly Bronteus ) with fan-shaped tail 
segments ; Calymene (capable of inrolling itself 
like a woodlouse) ; and Dalmanites (a large and 
handsome form with big compound eyes and a 
sharp tail-spine). 
Fig. 32. A Silurian Trilobite — Goldius greenii Chapm. 
From the mudstone of Lilydale, Victoria. 
This case is devoted to the Bivalved Crustacea Case 40. 
known as Ostracoda ; also the Pod-shrimps 
(Ceratiocaris), and the Sea-scorpion (Pterygotus). 
An interesting head-shield, referred to the 
primitive, jawless fish, Thyestes, is also to be 
seen here. 
Here the Graptolites of the Upper Ordovician slates Case 41. 
are grouped. Amongst these may be noticed the 
sigmoidal hydrosome of Nemagraptus, the calliper- 
and lyre-shaped Dicellograptus, and the tongue- 
shaped Glossograptus. The primitive Brachiopod, 
