Estates-tail

are either general, or special…. Tenant in tail-special is where the gift is
restrained to certain heirs … and does not go to all of them in general. And this may happen in several ways. I shall instance in only one: as where lands and tenements are given to a man and the heirs of his body, on Mary his now wife to be begotten; here no issue can inherit, but such special issue as is engendered, between them two; not such as the husband may have by another wife: and therefore it is called special tail.” 2 William Blackstone, Commentaries on the Laws of
England 113–14 (1766).
[Blacks Law 8th]