Oh come on, give it a little taste. hehe Where did your seeds come from? If they were certified organic seeds, or better yet, heirloom seeds, then
I wouldn't worry.
Cukes should be picked smaller anyway. When they grow too big they get tough. Same with summer squashes/courgettes.
You sure you didn't plant the Lemon cuke? They come out round like that. Did the seed area look like this
Next time when photographing, leave in the seed area. It helps for identifying. And if you garden regularly, don't toss the seeds in the trash.
Stick 'em in your compost pile.
I don't know where you are located, but I find these people really helpful
UBC Centre for Plant Research
They have a forum and are located in British Columbia, Canada.
If you don't want to do that, head to your nearest Botanical Garden.
There's a great one I wish I could see, Royal Botanical Gardens Kew in the UK, along with all the RHS sites.
Another great one around Montreal area. One in Buffalo, NY.