All birds have, like most reptiles, a well-developed third lid or "nictitating membrane," which moves from the inner canthus obliquely upwards and backwards over the cornea.
He also invented, with the same object, teeth whose fronts, instead of being parallel to the line of contact of the pitch-circles, cross it obliquely, so as to be of a screw-like or helical form.
The nostrils open obliquely at some distance from the end of the snout, and the head carries a crest of long hair.
The Indian flying-squirrel (P. oral) leaps with its parachute extended from the higher branches of a tree, and descends first directly and then more and more obliquely, until the flight, gradually becoming slower, assumes a horizontal direction, and finally terminates in an ascent to the branch or trunk of the tree to which it was directed.
The south-east trade-wind blows obliquely across the Atlantic Ocean until it reaches Brazil.