I aggree with your view on shellder but on cloyster you are way off.
Cloyster's 1st attack is flip coin. Heads=30+paralization Tails=nothing
All it is is horn hazard with the ability to paralize if heads for an
extra energy.
About being only American pokemon to defeat all fire with spike cannon,
which is flip 2 coins 30 damage times number of heads, Polywhirl can do
the same thing for an aditional colorless energy. And even then you have
2 flip 2 out of 2 heads. Dewgong and Gyrados can parilize if 1 heads out
of 1 doing 60 and 80 damage respectively, sot the next turn they can do
they're 50 damage, 100 to fire, attacks, doing same thing as polywhirl
and Cloyster except its over two turns, but then again the fire pokemon
won't be like to unparalize themselves. Don't forget none of this will
happen to the fire pokemon of Moltres, since he has no weakness. That
means a 70! damage attack is needed, NOT 60. And as of know, there is no
AMERICAN UNENHANCED REAL water pokemon that can do 70 in one turn. Sothe
rationgs should Shellder: 0.157 Cloyster 2.645