be found to agree entirely with the horns of the higher animals."[1]
The integument is more or less obviously divided in a vertical direction into thirteen segments, and each of these segments has been supposed to consist of four parts intimately united, which would make the whole case consist of fifty two pieces.[2] But the three most obvious divisions, manifest to the most cursory observation, are the head, thorax and abdomen.
The Head is very variable in shape, but most commonly spherical, either the longitudinal or transverse diameter predominating. It forms a kind of box, having an aperture before and behind: the former is occupied by the organs of the mouth, the latter by the muscles, &c., which connect the head with the thorax. The whole of the lateral superficies is occupied by the eyes. Particular regions of it have received names from the analogy which they are thought to bear to the parts of the head in the higher animals, but scarcely two authors agree in their nomenclature and definitions. Considered as a whole, the cephalic box may be regarded as the skull, (cranium) since it encloses what is regarded as corresponding to the brain of the vertebrata. The upper portion of the skull extending from the region of the eyes
