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If the principal vein descends on an incline and the cross-vein descends vertically, then a minor triangle is created having one obtuse angle or all three angles acute.

Nay, further, these same miners, if no stringer or cross-vein intersects the main vein so that they can follow it in their workings, even cross-cut through the solid rock of the hangingwall or footwall.

Basilar cross-vein: Odonata; crosses the basilar space.

Hypotenuses: in Odonata; the simple or broken cross-vein between media 4, and cubitus 1, forming outer boundary of triangle.

Oblique vein: in Odonata; an apparent cross-vein situated between M2 and Rs, distal to the level of the nodus and inclined obliquely, from its front end, backward and outward; in reality the basal part of Rs.