# Statistical test for 2 groups of proportions

I am hoping that I can get some advice on the best, or most appropriate, way to analyze a specific type of data.

I have collected data on brain volumes across two different species of mice, A and B. I want to compare subregions within the brain and know that one species is just bigger than the other so have larger brains in general. But, if I divide each subregion of the brain by total brain volume, I get proportional values. If I want to compare those values across the two groups, can I use a t-test? Obviously these aren't normally distributed, which is often claimed to not be a huge issue. The values will also be very similar in general within and between groups, and of course, the values across all different subregions within one subject will be correlated as they are a proportion of the total. I can't conceptualize if there are other issues, however. Any thoughts or advice would be greatly appreciated.

Here is an example of the data for one subregion, for example (though in my dataset I have about 100 samples in each group, I just didn't type out 100 rows):

A B
.01 .008
.009 .012
.012 .0075