Common Rorqual = fin whale (Balaenoptera physalus)
Sibbald's Rorqual or Blue Whale = blue whale (Balaenoptera musculus)

British mammals /
Date 1920-21.
Source http://www.flickr.com/photos/biodivlibrary/21269607064
Author Archibald Thorburn
Source: https://commons.wikimedia.org/wiki/File:British_mammals_(Pl._43)_(21269607064).jpg

The fin whale (Balaenoptera physalus), also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second-largest animal after the blue whale.

The blue whale (Balaenoptera musculus) is a marine mammal belonging to the baleen whales (Mysticeti). It is the largest animal known to have ever existed. Blue whales were abundant in nearly all the oceans on Earth but their numbers have been greatly reduced due to whaling.