“And if he were her mate? There would be the barb, that extension her sister had told her about that emerged from beneath the wide crest of a feline Breed male’s cock when he found his release inside his mate.”

 Lawe's Justice

and later: “He rubbed his tongue against her, much as she had rubbed hers against the hidden barb on the heavy crest of his dick. A slow, tasting rub that filled his mouth with the taste of her and the taste of the mating hormone.”

-S.G.