Mammillaria machucae is a form of Mammillaria spinosissima.
Mr. Chris Davies about M.manana/M.machucae......
Initially FitzMaurice published a description of a species called M. machucae, but this was actually a form of M. spinosissima. I am not sure what exactly happened, but somehow he published the details of what became M. manana under the name of M. machucae, but that wasn't what was intended.
When he published M. manana in 2006, he made no apology for earlier errors. But the damage was done, and many nurseries still use M. machucae rather than the later, but correct, name.
As he is an elderly man now, it was, I believe a genuine error, but one that still causes problems.
According to Thomas Linzen, not all plant sof M. manana have only white spines. Some, it seems, have reddish brown tips to the otherwise white spines."