According to Proclus an angle must be either a quality or a quantity, or a relationship. The first concept was utilized by Eudemus, who regarded an angle as a deviation from a straight line; the second by Carpus of Antioch, who regarded it as the interval or space between the intersecting lines; Euclid adopted the third concept, although his definitions of right, acute, and obtuse angles are certainly quantitative.
In the carpus the scaphoid and lunar bones are united.
Its elastic tendon runs directly to the carpus, forming thereby the outer margin of the anterior patagium, or fold of skin between the upper and forearm, which it serves to extend, together with the propatagialis brevis muscle.
All the bones of the limbs are separate, and those of the carpus and tarsus do not alternate; that is to say, each one in the upper row is placed immediately above the corresponding one in the row below.
In none of the existing, and in but few of the extinct types, are collar-bones, or clavicles, developed; and the scaphoid and lunar bones of the carpus are separate.