A further question relating to the legs, suggested by the Otisville specimen of S. cestrotus, is whether the second and third pairs were as short and as nearly equal in size as represented by Woodward and Beecher. Here again all the types which retain these legs; those of S. cestrotus, S. macrophthalmus, S. elegans and S. ornatus, give direct evidence that they also formed a posteriorly increasing series, the last being the longest and that, on the whole, they were much longer than represented in the restorations. The specimen of S. logani [text fig. 63] which served as the basis of the restorations exhibits a fragment of two segments of one of these legs attached to the body and is surrounded by two (three in first figure, 1864) detached anterior legs. The smaller of these undoubtedly represents the first pair of postoral limbs, as clearly indicated by its rapid contraction and the shortness of the segments. As the first pair Woodward introduced antennae and constituted as the second pair what we believe to be obviously the first, while the other, which has about twice the length of the former, to us represents the second pair. The third pair is only represented by the small fragment still attached. It is quite clear that there is considerable difference in length between the first and second legs and a still greater difference between the second and third legs. The relative lengths of the first and second legs are well shown in Laurie's type of S. macrophthalmus [text fig. 64] and the relative great length of the third pair is evident in S. elegans [text fig. 62] where it nearly equals the fourth pair and surpasses it in width. Looking back again, in relation to these legs, to Drepanopterus, the ancestor of Stylonurus, we find that there the first three pairs also form a series increasing in length backward.
The combined evidence, then, of the material at present available is that the legs formed an approximately continuous series, the anterior members being longer than hitherto supposed and the last two not so greatly surpassing the others in length and not of so nearly equal length. On the basis of these facts we have drawn a new reconstruction of S. excelsior, although only the first pair of legs of that species are known, using mainly our specimen of S. cestrotus for this reconstruction.
