Now, it often happens that, as in the last example given, the animal form, literally rendered, does not fill the panels satisfactorily. The head and the tail do not correspond and there is a lack of balance. In such cases two heads have been preferred. The body is given a uniform double curve and the heads are turned down, as shown in Figs. 268 and 269, or one may turn up and the other down, as seen in Fig. 270. The two headed form may also arise from imitation of plastic forms, as I have already shown. The example given in Fig. 268 is extremely interesting on account of its complexity and the novel treatment of the various features. The two feet are placed close together near the middle of the curved body, and on either side of these are the under jaws turned back and armed with dental projections for teeth. The characteristic scale symbols occur at intervals along the back; and very curiously at one place, where there is scant room, simple dots are employed, showing the identity of these two characters. Some curious auxiliary devices, the origin of which is obscure, are used to fill in marginal spaces. The shape given in Fig. 269 is so highly modified that it is not recognizable as an animal form, excepting through a series of links connecting it with more realistic delineations. It is perfectly symmetrical and consists of a compound curve for the body, with hooks at the extremities and two appended hooks for legs. The spots symbolizing the scales are here placed within the body, showing another step toward complete annihilation of the natural forms and relations. Three additional examples, showing still higher degrees of convention, are presented in Figs. 271, 272, and 273. The series could be filled up and continued indefinitely, connecting the whole family of devices in which dentals, hooks, spots, and circles occur with the alligator radical or with other reptilian forms confused with the alligator through the carelessness or ignorance of the decorator. [Illustration: Fig. 271. Highly conventionalized alligator derivative.] [Illustration: Fig. 272. Highly conventionalized alligator derivative.] [Illustration: Fig. 273. Highly conventionalized alligator derivative.] In looking over a large series of the vases it will be seen that the tendency of decoration is toward the zonal arrangement, the spaces being narrow and long, even when divided into the usual number of panels. As a consequence the motives tend to take linear forms. Parts are repeated or greatly drawn out to fill the spaces. This phase of conventional evolution may be illustrated by a multitude of examples. [Illustration: _a, b, c, d, e, f_ Fig. 274. Series of forms showing modification through use in narrow zones.]