Yes, the Baronetage is just what you think it it - a listing of the country's baronets.

The succession to titles is governed by the wording of the individual royal "Letters Patent" which created that particular title; for most English titles, the wording is "heirs male."

The Dugdale mentioned is Dugdale's "Ancient Usage in bearing of such Ensigns of Hounour..etc" (1682) and lists 159 baronets, of which The House of Elliot was one, one assumes. ;-)