The GPS is bouncy here. You are looking for the entrance to 333 Bay St. Specifically, you are looking at the left side (north) panel of the wall at the entrance. There is no need to go inside (unless you want to!).
***
General responses (e.g. "it's sedimentary because it has layers") will not be accepted. I don't expect you to be a geologist, but I do expect you to read the lesson, think about what you see, and apply some new learning in your responses.
Please submit complete answers to the given questions as soon as you complete the EC, and preferably through the messaging service rather than sending via email. I will read and reply to all answers submitted. Insufficient/inaccurate/missing answers may result in a deleted log. Thanks!
***
The Lesson - Tyndall Stone and Fossils
Tyndall stone is a dolomitic limestone quarried in Canada, specifically Garson and Tyndall, Manitoba. It is a cream-coloured limestone with a pervasive mottling of darker dolomite. The mottling gives the rock a tapestry-like effect. Famous Canadian buildings that use Tyndall stone in their construction include the Parliament Buildings in Ottawa and Canadian Museum of History in Gatineau.
Tyndall stone is mined from the Selkirk Member of the (late) Ordovician Red River Formation. The Ordovician period is dated to approximately 485-443 mya (early (485-470 mya) - middle (470-458 mya) - late (458-443 mya)). The Red River Formation has 4 distinct layers (members) from top to bottom - Fort Garry, Selkirk, Cat Head and Dog Head. The Selkirk and Dog Head members are the dolomites that are fossiliferous.
Invertebrates, specifically molluscs and arthropods, dominated the oceans during the Ordovician period. The Great Ordovician Biodiversification Event significantly increased the diversity of life. Fish, the first true vertebrates, continued to evolve, and those with jaws may have first appeared late in the period. Life on land, however, had yet to diversify. Interestingly, about 100x as many meteorites struck the Earth per year during the Ordovician as compared with today.
As mentioned, Tyndall Stone is highly fossiliferous and the fossils contribute to its aesthetic appeal. Fossils common to this type of stone include gastropods, brachiopods, cephalopods, trilobites, corals, and stromatoporoids, to name a few. Fossil burrows in Tyndall stone are called Thalassinoides. My new, personal favourite fossils in this stone are the receptaculites. This is the name (genus) given to an extinct group of conspicuous benthic marine genera that peaked during the Middle Ordovician. The group's phylogenetic origin has long been obscure, but the current understanding is that the Receptaculitidae were calcareous algae. They have an interesting shape and remind me of a sunflower. These "sunflower coral" fossils can usually be identified by the intersecting patterns of clockwise and counterclockwise rows of plates or stalk spaces.
Images (all from Wikipedia):
Gastropods (snails) 
Brachiopod with a worm tube attached
Cephalopods (3 examples)
Trilobite 
Thalassinoides
Corals (3 examples)
. 
. 
Stromatoporoids (sponges, 3 examples)
Receptaculites (extinct calcareous algae, 2 examples)
***
Questions - group answers will not be accepted, so please send as individual responses.
1. There are at least 4 fossils of significant size at GZ. Select at least 2 different types of fossils and:
a) Describe and measure each of your selected fossils;
b) Include a photo of each of the fossils with your answer (do not post);
c) Based on your observations and the lesson, identify each of the fossils.
2. Based on the information provided in the lesson, what do you think caused the mottling in the stone? When did this mottling likely take place?
3. Based on your observations of the fossils, how old is this particular example of Tyndall stone? What evidence did you use to come to this conclusion? Please note, "Ordovician" is not an acceptable answer - you need to be more specific with a date and provide a reason based on your observations at GZ (in combination with the information in the lesson).
4. To demonstrate that you were on site, take a photo of you/your GPS/your caching name in front of the 333 Bay sign. Post this with your log.
Thank you for visiting this EarthCache! I look forward to reading your responses.