delete pairs of data out of a range : I'm trying to delete from a matrix like this:

           x        y
      37.013930	048.775597	
      43.015619	348.803652	
      06.017302	349.831709	
      05.018978	348.859767	
      37.020646	300.887827	
      23.022307	348.915887l
          .           .
          .           .
          .           .
 the data pairs (x, y) that are not in the range (44,350.5)=>(4.5,35.8). Does anyone know how to do it?