xscheme-startup-message

xscheme-startup-message is a variable defined in `xscheme.el'.
Its value is

"This is the Scheme process buffer.\nType \\[xscheme-send-previous-expression] to evaluate the expression before point.\nType \\[xscheme-send-control-g-interrupt] to abort evaluation.\nType \\[describe-mode] for more information.\n\n"

Documentation:
String to insert into Scheme process buffer first time it is started.
Is processed with `substitute-command-keys' first.

You can customize this variable.