You need an extra pair of parentheses, which you must escape with backslashes to make them literal characters:
regex = r'<span class="SciName">\((.+?)\)</span>'
You will use this as in:
import re
text = '<span class="SciName">(Acanthastrea bowerbanki)</span>'
regex = r'<span class="SciName">\((.+?)\)</span>'
m = re.match(regex, text)
print m.group(1)