What is "tortoiseshells"

Usage examples of "tortoiseshells".

Are you aware, my dear, that insofar as I have been able to decode it, the information in the patterns of tortoiseshells is of a com­pletely different nature in your world than it is in mine?

Tabbies, blacks, tortoiseshells and indeterminate patches, stripes and splotches — and there a sudden flash of white.