Probably the majority of the remains found are the cast exuviae from the frequent moltings of growing individuals. The recent Limulus may take as long as eight years to reach maturity when, with the last molt, the clasping organs of the males appear. It is therefore probable that the eurypterids also were relatively slow in growth and it is a fair presumption that the great majority of the specimens found represent immature individuals. They are mostly dismembered and among the fragments of the integument, head shields with the first body segment attached are especially frequent.
 Figure 3 Eurypterus fischeri Eichwald |
We consider it possible, or even probable, that the molting took place as in Limulus through a rent formed back of the frontal doublure of the head shield, through which the animal crawled out. Not only have specimens been found, as the type of plate 6, figure 1, where there is a gaping rent along the front edge of the head shield, but it is also inconceivable that the animal could otherwise have freed its legs so as to pull itself out of its old integument.
The test was thicker on the head shield for that is always less wrinkled and has retained its form better, and it was on the whole, thicker on the dorsal than on the ventral side. The appendages were also clothed with thicker test and the basal segments which attended to the mastication of the food were furnished with an especially thick cover. The postoral plate was likewise thick and is always well preserved.
Scales. The test or exoskeleton is characteristically ornamented by scale markings. On the head shield these consist of tubercles which are mostly simple thickenings of the test, but in some forms, as Eurypterus pustulosus, may grow out into large hollow wart-
