There are about 75,000 different types of fungus, the spores of which are floating in front of you're eyes right now. I suggest that you consult with a mycologist. Ah! I just read your profile. Most fungi are identified via morphological examination of it microscopic structures such as spores and conidia, fruiting bodies such as you show are only part of the process of identification. You should educate youreself on how to collect samples for microscopic examination and the means of which to identify them this way. This will keep you up for a couple of nights but you will be the better off for it:)

It looks like a cup fungus (Pezizaceae).

Many genera and species still to chose from.

Chloe, try www.ispotnature.org for your ID queries, lots of experts there.

Puzzled that this was growing on sand. There must have been some sort of organic material to support it. Peziza repanda grows on plant debris, or a larger form on sawdust. P. versiculosa grows on manure or compost heaps. These are the two nearest the colour of the ones in your photo. It is difficult to identify many fungi just from a photo of the fruiting body. If Ispot can help you it would be interesting if you would add what they say as a comment on your question!

Just another thought - if this is for a seed bank exercise are fungi relevant, not growing from seeds?