Coxal pores are found on the coxae at the base of the last pair of legs. In most species these are located on the ventral surface, but also additional pores on the anterior surface of a few species.
In Geophilomorph centipedes these tend to fall into two main patterns:
1) Numerous pores scattered widely over the entire ventral surface of the coxae (e.g. Haplophilus, Strigamia, Pachymerium, etc).
2) Several coxal pores arranged in a 'wobbly' row along the boundary between the coxa and the metasternite. In a few species there is also one isolated pore beyond the row (arrowed in far right image). In some species this, diagnostically, can be just as 2 coxal pores on each coxa (e.g Schendyla and Geophilus truncorum).
3) There are non-conformists that don't abide by these rules (e.g. Henia and Stenotaenia)!