326 NEW YORK STATE MUSEUM 
The specimens were discovered by Dr L. B. Welch, and the largest 
fragment, a nearly perfect endognathite, remained in his collection. <A 
fragment of a second endognathite, and a large quadrangular fragment, 
regarded as the dorsal part of a postabdominal ring segment, passed into 
the possession of Mr 8. A. Miller, by whom all three specimens were described 
and figured as Megalograptus welchi [Cincinnati Quar. Jour. 
Se1., 1874, 1:343]. The two specimens acquired by Mr Miller are now 
in the Walker Museum, at the University of Chicago. Other fragments 
have been found, but none of these ‘give any additional information. It 
is probable that if at the time of discovery the fragments at hand had been 
recognized as that of some large eurypterid, much more could have been 
obtained. The collectors were after crinoids, and by the time that the 
black filmy fragments had been recognized as of interest, almost the entire 
specimen had been irretrievably destroyed. 
The large endognathite belonging to the Welch collection was not 
thoroughly cleaned by Dr Welch, and I have taken great pains to deter- 
mine its exact outline. In this, there has been fair success except in the 
case of the basal joint, where a part of the thin chitinous epidermal layer 
had already scaled off, and where the underlying rock offered no trace of 
an impression. In the case of the basal joint, therefore, the outline pre- 
sented is that of the specimen in its present condition, and not of the 
perfect specimen. The specimen may be described as follows: 
If that part of the specimen numbered 1A and 1B in the accompany- 
ing figure be the basal joint, then the masticatory edge does not preserve 
distinct serrulations. The posterior proximal corner is prolonged into a 
spinose projection. The posterior margin is not well preserved; at the 
distal end there is a minute denticulate projection. If the large segment 
here considered as a single basal joint in reality consists of two joints, 
as the reentrant angle both anteriorly and posteriorly seems to indicate, 
no trace of jointing could be found on the surface of the specimen. 
The line of separation between the first and second joints is distinctly 
shown, but the distal corner along the posterior edge of the second joint 
is not well preserved, and its form, therefore, remains in doubt. Along 
the anterior margin of the second joint there are prominent spines. Of 
these, the spine nearest the distal margin is 15 mm long; a small spinose 
projection, 3 mm in length, appears to overlap the proximal end of 
the base of this spine. Opposite the middle of the second joint 
there is a pair of spines, apparently united for a short distance above 
their bases. The proximal edge of this pair overlaps, near the base, the 
distal edge of another spine, only 9 mm in length; and the latter, in turn 
overlaps a much greater part of still another spine, at least 6 mm long. 
The distal corner of the posterior margin of the third, fourth, fifth 
