which undoubtedly has affected the specimen, figure 9. Larger collections may, however, bring out the fact that we have here to deal with varietal differences.
Besides the carapaces and attached first tergites, fragments of other parts of the test of a Stylonurus occur at Otisville and their prominent rows of tubercles suggest that they belong to this species. Most easily recognized among these are the tergites [pl. 53, fig. 4, 5]. Besides the posterior row of tubercles borne on a high crest, these show a parallel middle row of less distinct tubercles, which also crown a narrow ridge. In some a row of smaller and less distinct tubercles is seen posteriorly of the other and alternating with it. Further, densely tubercled metastomas of the shape of that reproduced on plate 53, figure 1 occur not infrequently. They probably also belong to this species. Portions of legs with longitudinal rows of tubercles [fig. 7] suggesting their reference to this species, have also been observed.
A single entire individual has been observed and, judging from the subrectangular outline of its carapace and the size and position of the eyes this probably represents S. myops [pl. 52, fig. 6]. Unfortunately its test is reduced to a film that retains no sculpturing and shows nothing but the outline. The most characteristic features of the specimen are its relatively compact form and the small length and great width of the abdomen and the long spurlike epimera of the segments, both of the preabdomen and postabdomen. The total length of the specimen is but 55 mm, its greatest width however amounts to 20 mm.
Such spurlike epimera of equal relative size are possessed only by the large S. scoticus from the Old Red sandstone. Curiously enough that isolated and strange form is like S. myops in outline of carapace, the approximate position of the eyes and the sculpture of the tergites. It seems probable therefore that S. myops, when fully known, will prove a representative of the subgenus Tarsopterus of which S. scoticus is the type.
Of the telson of the species, but a small proximal portion is preserved.
