What species of red round watermelon is this

I don't believe there is a fool-proof way to determine 'ripeness' without taking a slice out of it. The best you can do is look for certain signs:

• Ripe melons have a hollow sound when you tap or slap the outside
• Look for the patch where the melon would have been on the ground (called the field spot). If it's a yellow colour its probably ripe, if it's white, it's probably not.
• It should feel relatively heavy when lifted
• Weird areas on the skin aren't necessarily bad. insects may have tried to start eating the fruit because it is ripe, but have only marred the surface.

Unfortunately, melons don't continue to ripen once picked, unlike fruits such as apples, bananas etc. which contain ethylene. As a tip don't store melons with these kinds of fruit, they may well go 'soggy'.

Extra: NYtimes video on picking the right watermelon.

The way that i found to juice mine is leave the rind on, mash the melon to bits inside of it, cut a spout in the rind for easy pouring, line my stock pot with chese cloth (although i'm sure a lot of other things would form a great strainer), then just pour the whole thing into the stock pot. I then wrap the cheese cloth up and tie it off with a rubber band. Then you place a plate on top of the cloth and weight it down with a book. Check back every one or two hours to tighten the cheese cloth up and you end up with a lot of juice and none of the nasty bits. I also tend let the contraption sit in the fridge while it does it's work but it will work just fine on a counter top. The set up takes me about ten minutes.