The membranous cover of the ovum at ovulation is
corona radiata
The ovum is enclosed by the inner thin, transparent, non-cellular coat zona pellucida and outer thick coat corona radiata. It is formed by follicle cells adhering to the oocyte before it leaves the ovarian follicle. During fertilization sperm first comes in contact with the corona radiata and then zona pellucida to reach the plasma membrane of the egg(ovum).