At the base of each leg are several chitinous plates (fig. 28), upon which no small labour has been bestowed by different anatomists. They are arranged so as to form two joints intermediate between the coxa and the sternum, and these two joints admit of a hinge-like movement upon each other, while their other ends are firmly attached to the coxa and sternum respectively. (Compare III and IIIA, fig. 28.) These parts in the Cockroach may be taken for two basal leg-joints which have become adherent to the thorax. In other cases, however, they plainly belong to the thorax, and not to the leg. In the Mole-cricket, for instance, similar plates occur; but here they are firmly united, and form the lateral wall of the thorax. In the Locust they become vertical, and lie one in front of the other. Most authors have looked upon them as regular elements of a typical somite. They regard such a segment as including two pleural elements--viz., a dorsal plate (_epimeron_), and a ventral plate (_episternum_). We have already (p. 34) given reasons for doubting the constancy of the pieces so named. It is not inconvenient, however, to denote by the term _episternum_ the joint which abuts upon the sternum; for the joint which is applied to the coxa no convenient term exists, and its occurrence in Insects is so partial, that the want need not be supplied at present.[70] Both joints are incompletely subdivided. In the first thoracic segment of the Cockroach they are less firmly connected than in the other two. [70] The nomenclature adopted by Packard (Third Report of U.S. Entomological Commission) seems to us open to theoretical objections.