In an action to foreclose a mortgage, the appeal, as limited by appellants' notice of appeal and brief, is from so much of an order of the Supreme Court, Suffolk County, entered December 29, 1977, as denied the branch of their cross motion which sought to dismiss the complaint as against them on the ground of usury. Order affirmed insofar as appealed from, with $50 costs and disbursements. Assuming, arguendo, that the agreement to extend the purchase-money mortgage was usurious, it would not invalidate the original obligation under the mortgage (see Gross v Lichtman, 55 A.D.2d 670; Marks, Maloney Paperno, Mortgages and Mortgage Foreclosure in New York, § 251, p 353). Latham, J.P., Suozzi, Gulotta, Shapiro and Cohalan, JJ., concur.