Page:The Eurypterida of New York Volume 1.pdf/304

 considerably the longer. The breadth and the mean length are each about 18 mm. The dentate border is slightly produced and in length is equal to about one half the breadth of the joint. The dentation begins at the front end with an isolated, blunt tooth pointing forward, followed by sharp, curved teeth of small size which grade posteriorly into fine, hairlike bristles. The anterior side of each joint from the second to the sixth inclusive, is arcuate. The posterior sides of the second and third joints are straight, of the fourth, fifth and sixth, concave. The distal end of each is at right angles to the long axis. The second joint is narrower (14.5 mm) than long (23 mm); the third just twice as long (28 mm) as wide (14 mm); the fourth a little longer than the preceding (30 mm) and less than half as wide (7 mm). Along the concave, posterior side of the fourth are articulated five, long, curved, striated spines, nearly perpendicular to the joint. At the distal end of the series there is an indication of another. The most complete of these spines is 16 mm in length. The fifth joint is 16 mm long and 6 mm wide. Near the anterior end of the posterior edge it carries the stump of a large spine followed by the sockets of four more. The sixth joint bears the basal portion of three spines, but is so crushed and foreshortened that neither the original number of spines nor the length of the joint can be determined. Judging by the taper of this arm, there may have been two more joints.

The remnant of another appendage appears to be part of the proximal four joints, and measures 32 mm in length. From its robustness, it seems to have belonged just in front of the last mentioned. The peculiarities of these joints are their shortness and their thickening at the articulations. The joint, which on the tablet lies nearest to the large arm, is a little inflated and, though very imperfect, has the appearance of being the coxal joint.

The two other appendages of this group are robust and short. One is tolerably complete, apparently lacking only the dentate border of the coxal joint. It is 38 mm long and consists of seven joints. The coxa is large and globose. Each joint from the second to the fifth carries on the posterior edge a pair of short, stout, distally directed, lanceolate spines, averaging 2.5 mm long and nearly half as wide. Joint two is broad and very short. Joints three, four and five are subquadrate and successively smaller. Joint six is nearly one and one half times as long as broad and at the end bears two distally directed spines, one anterior, the other posterior. The seventh is long and clawlike, slightly inflated at the base. The other appendage is so crushed and folded that little can be determined by it. However, from the larger size of the coxal joint, it is probable that its position on the body was behind the more complete. The spines preserved on it, like those of the smaller appendage, are short and lanceolate.