Page:The Eurypterida of New York Volume 1.pdf/54

 observable in many other specimens [as pl. 7, fig. 7]. The oar blade is entirely smooth, without scales or hairs. The turning of this oar into a vertical position in the backward stroke probably took place mainly between the sixth and seventh segments.

The material before us is competent to throw some very interesting light on the development of this swimming leg. Where typically developed, as in Eurypterus, it consists of the large basal segment, which is

followed by two ringlike segments, a longer subtubular segment (the fourth), and two shorter segments with triangular section, flat underside, sharply keeled anterior edge and expanded distally. These segments