opposed sides this arrangement would be especially desirable in highly fractured carbonate zones the circular cross sectional area at the tip of probe 14 being relatively small limits the sampling area for the fluid recovery the present invention provides in the alternate embodiment of fig9 and 10 a slotted probe 40 in which tube 42 telescopes from housing 12 in the same manner as probe 14 but includes a flared end 44 forming an elongated aperture or slot 46 in an arcuate flange 48 in its simplest form probe 40 resembles an oblate funnel the curvature of flange 48 approximates the curvature of the borehole at the probe position and can be fitted at the surface to conform to bit size and anticipated borehole configuration however a resilient packer seal 50 may be fixed to the face of flange 48 to accommodate both circular and elliptical bore configurations of a drill hole some of the many advantages of the invention should now be readily apparent for example a formation tester is provided which self orients the sampling probe at the area of optimum permeability for optimum recovery of diagnostic fluid samples from subsurface formations and which can be readily adapted to existing formation testers a method is disclosed which assures optimum recovery of fluid samples by orienting the probe along the.