It is proper to say here that the restorations of S. logani and S. excelsior have always looked unnatural to us in leg construction, because it is not apparent how the two very different sets of legs could have been used harmoniously. Woodward and Beecher were not in accord in their opinions as to the use of these legs; the former considered the long legs as the swimming feet [see his description of S. logani] and the short ones as the walking feet, while Beecher per contra considered the long legs as the crawling feet [see 1900, p. 149]. As to the latter conception, it is unintelligible to us how the creature could have balanced itself on these four legs or could have taken up its food without correspondingly long prehensile organs, much like the chelae of Pterygotus and those of the recent sea spiders. The short anterior legs of the restoration would seem to have been hardly competent to propel the huge body in swimming and their position at the front of the carapace would have scarcely allowed their effective use for walking without the assistance of the other legs.
The gradually lengthening series of legs suggests to us that they, all combined, were functional in crawling, the long hinder pairs, on account of their stronger curvature and backward direction, reaching the same level as the shorter forward pairs with their terminal claws, thereby carrying the body as it is carried in nearly all crustaceans and arachnoids, on four or more pairs of legs.
There is a difference of opinion as to whether the last pair or pairs were the more active in swimming, as in the other eurypterids, or the first three pairs, as suggested by Beecher. On one hand analogy with the other eurypterids would indicate the use of the last pair of legs as swimming organs, and it would constitute a wide departure if this group reversed the functions of the fore and hind limbs. On the other hand, these hind legs show none of those characters which naturally accompany a swimming function, such as a widening of the joints and an intricate articulation insuring rigidity of the legs, while the preceding legs, in some species as S. cestrotus, are provided with a dense fringe of contiguous
