I'm unsure if this is a bug or if I'm missing something here. I've been wandering around attacking undead things in Newgate Prison, when I spotted a Shrieker (looks like a Banshee) and attacked it. I used a single Monstrology Undead card as I had two Shriekers, and you can see via the picture that it said I had collected. But the information in the text box to the left said I hadn't and that I had the wrong monster type? I didn't get Shrieker added to my Tome.
Image here: (Link to image removed as it is against The Rules. ~Dworgyn) Monstrology Level: 7
are you sure that the entity that you defeated was an undead? Either way, I think that it is a glitch. It usually does not say that it has collected the animus unless it actually collects the animus.