[R] Categorizing Lines

[Fabio Murtas]

Hi all, i have a dataset of 3D coordinates and can't figure out how  
to' tell R which One Are the individuals:

I have 3 columns which i named x,y and z
And then i have 2607 Lines, but each specimen is 33 Lines (79 specimens)

How can i tell R to' categorize individuals every 33 Lines?

Thanks in advance