Norwich Castle Museum, 115 
The Slugs, although not attractive in appearance, are 
very interesting animals. ‘They possess only a slight 
internal shell, which assumes the form of a thin 
plate protecting the breathing organs. 
There are other very remarkable species, which it 
would be desirable to mention did space permit, such 
as the CycLosromip#, which have a spiral shelly 
operculum ; the Bubble Shells (4z//2) ; and the curious 
Limpet-like Chinese-umbrella shells (Umbrella). ‘The 
numerous section, NUDIBRANCHIATA, or Sea-Slugs, 
objects of great beauty, are without shells, and therefore 
not represented in the collection. They are found 
under stones and sea-weeds in tide pools on every 
shore. We must pass on to the genus, “/ya/ea, one of 
the PTEROPODA, the doubtful position of which 
has already been mentioned. /yalea tricuspidata, the 
only species in the collection, is a curious globular 
shell with a terminal spur, on either side of which is a 
smaller spur, each of the latter being supplemented by | 
a long tooth-like projection ; the animal protrudes two 
large wing-like fins from its apex, which correspond 
with the foot of the Gasteropod. These creatures 
occasionally swarm in the open seas, propelling them- 
selves with their wing-like appendages. Nor can we do 
more than simply refer to the BRACHIOPODA (now 
separated from the Mollusca by modern Biologists), a 
very ancient family, fossil-forms of which are distributed 
through all the rocks of marine origin, but are most 
abundant in the Devonian age. Some 1,ooo fossil 
species are recognised, but the recent representatives, 
so far as they are known, do not exceed seventy. 
From their peculiar form they are known as ‘‘ Lamp 
Shells.” 
The third class, or main division of the Mollusca, 
is that of SCAPHOPODA, consisting of only one 
family, DenTaLID#%, with a simple genus, Denfalium, 
