def makeDestNameOld(baseName, sourceName):
	"""
	Given a baseName, and a sourceName of the form 'abc_1234.mda' return
	the string '<baseName>.1234'.
	"""
	# assume only one underline character
	root, right = sourceName.split("_")
	# assume only one "." character
	index, ext = right.split(".")
	return("%s.%s" % (baseName, index))