If you look around Leeds, there are plenty of buildings, and there is a wide variety of stones which are used, there are also a number of EarthCaches which describe the types of stone. We are here to look at some fossils. Yorkshire has a variety of good spots for fossils, from the Corals up Littondale, to Brachiopods near Kettlewell, to fossil plants around Ilkley and Baildon, but these places are not easily accesible to all, and some folk may be worried about heading up to these spots, after all, we are not all hillfolk 
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The rock which makes up this building is limestone, which is a sedimenatry rock, formed many millenia ago, in a shallow tropical sea, from the accumulation of shells of dead sea creatures, which gradually accumulated over time. Its is still possible to see evidence of these sea creatures in fossils. What we are looking for here are bivalves, inparticular two different types. Now, you won't immediately spot them, it is not T rex, or some large shell fossil, it is time to look closely at the blocks of stone.
A bivalve is a mollusc which lives within two hinged shells, and they tend ot be filter feeders. Modern examples are oysters, mussels and scallops. Many bivalve fossils are disarticaulated, which means you can only see one shell, as the two shells tend to seperate after death, since the muscle that formss the hinge decomposes and looses its integrity, but at times it is possible to see articulated examples, which means you can see the outline of both shells.
So what types of bivalve can be seen in the fossil form:
Oysters. These tend ot have an irregular wavy shape.
Plicatula damoni. These shells have small spines aligned along the shell, so as to anchor themselves to the seabed. The spines can be seen when looked side on, though you need to look closely to see them.
Camptonectes lamellosus. These shells are smooth, with no spines, but tend to taper at one end, this means that they narrow at one end.
This being an earthcache, in order to log it, I ask that you answer some questions. Please send them to me, and do not include them in your log. You can send them to me by using the message facility or email, both of which can be found by looking at my profile. Alternatively, if you see me at an event, you are welcome to discuss your answers over a drink. PLEASE REMEMBER THIS IS NOT MEANT TO BE A STRESSFUL ACTIVITY, IT IS MEANT TO BE EDUCATIONAL AND ENJOYABLE. I am not one of those folk who will make you feel like you are at school, or doing some type of masters degree. I show you these fossils, because it gives me joy to do so.
1. Please examine the rock closely, it may take you a while to see the fossils but they are there:
(a) Please find the Plicatula damoni fossil - is it articulated or unarticulated|? How long is it? Is it straight or wavy? Are the spines equally distributed along its body, or more at one end?
(b) Please find the Camptonectes lamellosus fossils - is it articulated or unarticulated? How long is it? How wide is the shell in mm?