A dwelling for not over one family, in which may be carried on, by members of the family occupying it, professional occupations, such as medicine, surgery, dentistry, law or architecture. Such uses must, however, be confined to 1/4 of the floor area of the residence building, and in no case shall it be conducted in a basement or cellar or in an accessory building. No display or advertisement of any kind, other than one ordinary professional nameplate not greater in area than one square foot, may be displayed. The Board of Appeals shall have power to determine what is a profession or occupation permitted under this section.