Page:The Eurypterida of New York Volume 1.pdf/30

 was sharply bent and the angulation has produced a distinct protrusion on the dorsal side of the last segment [ pl. 75].

4 The scales are not found on the telson spine, except the anterior swollen portion where the extensors and flexors were attached, nor on the broad, solid oarplates of the swimming legs, while they are present on the leg segments, frequently in distinct longitudinal rows which in some cases develop into regular continuous entapophyses on the inside of the integument, as in the powerful arms of Dolichopterus [ pl. 43].

5 On the postoral lip (metastoma) the scars are most strongly developed on the side that is turned toward the body and held by muscles.

6 The prevailing form of the scales is that of a V or a crescent pointing backward, and this shape, together with the fact that the integument is distinctly thicker and darker along the edges of the scales, is indicative of their function, since the muscle scars here, as among mollusk shells, are marked by their thickened edges. Forms with thicker integument, as, do not exhibit any scaly sculpturing on the outside.

7 The scales are well differentiated from the tubercles which are scattered among them [see test of Eusarcus, pl. 35, fig. 4] and on those parts where the thickness of the integument prevents the appearance of scales over the surface, as on the carapace, these tubercles alone are observed. Similarly the serrations of the edges of the rudder plate of the swimming legs, of the epimera of the abdominal segments and of the telson are independent of scales. But it appears that the spinules on the dorsal crust originate from scales, we surmise from a lengthening of the point of the angle of the V. In,   and  , as well as  , but a single transverse row of such spines is developed on each segment. In  the longitudinal series of scales on the postabdomen over the intestine show a strong tendency to develop into overlapping spinules and in the Carbonic subgenus Anthraconectes all scales possess this tendency.