Probably C. wendtii or something similar. Don't freak if some or all leaves melt after you divide & replant. They don't like being messed with and may melt. Just remove the goo and leave the roots, they'll come back.
It will be tough to be sure which species you have. Many crypts ar quite variable in appearance as a result of even minor changes in lighting or nutrient profiles.
For example - I've only bought 1 C. wendtii (brown), ever. I grew it out in a 5g, moved it all to my 46g and grew it out some more, then returned a plantlet to my 5g when I culled & sold about half of them. Comparing pictures of the original 5g growth to what's in the 45g now and to the plant I put back in the 5g - you'd swear that they were pix of 3 totally different species.
this was the first plant i ever tried to grow. at the time i was unaware that they would "melt" if split. i brought it home, split it up into three different bunches and planted it. i thought i had killed it! easy to grow though. i dont give it anything at all in the way of ferts and i have a standard aquarium bulb