27 
A Silurian Limpet of fine ornamentation is shown here, case 36. 
Helcionopsis elegantulum ; it occurs in the limestone 
of Cave Hill, Lilydale. Another notable shell from 
the same locality is the trumpet-mouthed Trema- 
tonotus, which has a series of openings along the 
back, reminding one of Haliotis, the ear-shell. 
Bellerophon is also a noteworthy genus a very 
form of which, B. cresswelli , has a large bell-mouth 
and prominent dorsal keel. Pleurotomaria and 
the allied Phanerotrema belong to a group whose 
living descendants are very rare, Pleurotomaria 
being known only by a few individuals at the present 
time. 
Fig. 30. A Silurian Slit- band Snail — Phanerotrema australis 
Etheridge fil. 
From the Cave Hill Quarry, Lilydale. 
