I'm back, but don't get too excited, unless you happen to like manta rays and rhinos. It's one more step forward in the interminable slog through the Monster Manual.
MANTA RAY: Manta rays first appeared in Supplement II: Blackmoor. In their original appearance they could be up to 75' across, but here they are only about half that size. Statistical changes are as follows: Number Appearing has changed from 1-4 to 1; Armor Class changed from 5 to 6; Movement raised from 12 to 18; and Hit Dice lowered from to a range of 8-11. Their bite attack now deals 3-12 damage instead of 1-6, and the Manta Ray has gained the ability to swallow its victim whole (this ability was mentioned in passing in the original entry, but it is only now concretely defined). It's tail attack has also been changed. In its original form, a PC hit by the tail required a save vs. paralysation, with no damage indicated (although it is said to be treated as a mace, so I guess it does 1-6). Here the tail has been given a damage range of 2-20, and will stun its victim for 2-8 rounds if the save is failed. Like many of the monsters from Supplement II this is a case of a hazily defined monster getting a huge dose of clarity.
PUNGI RAY: Speaking of clarity, this entry begins by actually defining what a Pungi Ray is, something Supplement II never bothered to do. I realise that it would be easy enough to look the creature up in real-world books, but it never hurts to have the info on hand in the Monster Manual. A Pungi Ray is a ray with spines on its back that hides on the sea bottom. Anyone who steps on one might get stabbed by a spine, and must save vs. poison or die. The main difference between the Monster Manual version and the original is a matter of sanity: a character falling on a Pungi Ray in the original version would be subject to 20-30 attacks; now the number is 2-8. Statistically, Number Appearing has changed from 1-4 to 1-3; Armor Class from 6 to 7; Movement from 6 to 12; and Hit Dice from 6 to 4. It has also lost the ability to attack as a giant leech should it get on top of an adventurer. Gary really nerfed this one.
STING RAY: As far as I can tell, this creature hasn't appeared in D&D before this. It's a much smaller ray, with a tail that can paralyse its victim. A nice option for lower-level characters.
REMORHAZ: This monster first appeared in The Dragon #2. Statistically it has changed little: originally it could have Hit Dice of 6, 10 or 14, but now it ranges from 7-14. Its bite damage gets a minor tweak, from 3-36 to 6-36. It retains the same whopping Magic Resistance of 75%, and the ability to melt non-magical weapons that strike its superheated back. Said back is now much deadlier to adventurers, though, as it is now said that any character touching it takes 10-100 points of damage. The Remorhaz also gains the ability to swallow opponents whole on a natural 20, which incinerates and kills them instantly. Fighting one of these doesn't sound too enticing, but in true Gary fashion he tempts you by giving their eggs a value of 5,000 gp each.
RHINOCEROS: The common Rhinoceros has been mentioned as a possibility to be summoned by the Conjure Animal spell in Supplement I: Greyhawk, and has also appeared in the Wilderness Encounter tables in Supplement III: Eldritch Wizardry. It gets stats here for the first time. I expected them to be tough, but 8-9 Hit Dice is well above what I was thinking. There is a single-horned variety and a two-horned variety, the latter of which deals more damage. Their main form of attack is a charge which deals double damage, and also the ability to trample "any opponent which is low enough for this action", i.e., Hobbits.
WOOLLY RHINOCEROS: As above, but slightly tougher and significantly woollier. I believe that their only appearance has been in the Wilderness Encounter tables of Supplement III.