proportions generally agree in the two species. Even more like E. scorpionis is the single known specimen of E. obesus from the same Lesmahagow horizon, and it has been suggested by Woodward, who described the species, that E. obesus may possibly represent the young of E. scorpioides; certainly E. obesus looks very much like a young individual of E. scorpionis figured by Clarke and Ruedemann from the Bertie (Figs. 24 and 25). Thus there is close relationship between the two species from Lanarkshire and the one from the Bertie.
The last species from the Ludlow fauna, and the only Eurypterus yet found therein is E. lanceolatus Salter. As Sarle, Clarke, and
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| Fig. 24. Eurypterus obesus H. Woodward. ✕ . (After Woodw. 1878, pl. XXX, fig. 8) |
Fig. 25. Young of Eusarcus scorpionis Grote and Pitt. ✕ . (After C. & R. 1912, pl. XXXVI, fig. 1) |
Ruedemann have pointed out, this species has many points in common with Hughmilleria and either belongs to that genus or is transitional to it. The form of the body, shape of the carapace and of the telson, marginal position of the eyes, the relative proportions of the somites, and details in the appendages, all point to affinities with Hughmilleria socialis Sarle, from the Pittsford (figs. 26, 27). Such a relationship seems a little disconcerting at first, in view of the fact that the Pittsford sediments and fauna came from Appalachia, while the Ludlow was a derivative from Atlantica and should have a fauna essentially distinct from the former. Indeed, with the exception of this one species, the members of the Ludlow fauna show no relationship to any species from the faunas of Appalachia. We have here, as a matter of fact, one of the "anomalies" of distribution
