236 NEW YORK STATE MUSEUM 
broad, well rounded lobes on either side of the broad median sinus. Post- 
lateral angles obliquely truncated and rounded. The second sternite has 
also the posterior angles of the median cleft well rounded off, while in the 
succeeding plates the posterior margin is continuous. 
As the specimen reproduced in plate 35, figure 5 shows, the sternites 
were not only very convex in outline, but also highly arched, forming a 
high ventral vault. 
The postabdomen forms a slender tail that sharply contrasts with that 
of the extremely broad preabdomen. The curved telson spine combines 
with the long tubular postabdomen to produce the singularly scorpioid 
aspect of the tail. 
The first postabdominal segment which closes the interval between 
the broad preabdominal and the following narrow segments resembles the 
former in the dorsal and ventral aspects, as in other eurypterids. Itisa 
short ring, about three times as wide as long, contracting posteriorly by 
one third of its width. The other segments are practically tubular. Their 
relative length increases so strongly backward that while the second seg- 
ment is not quite half as long as wide, the last is six times as long as 
wide. The numerous marginal wrinkles and the form of the median 
portion of some less compressed segments indicate that the section of 
the last segments was nearly or quite circular. | 
The telson is a curved, stout spine, half as long as the postabdomen 
or equal in length to the last two segments. Its first two thirds are 
gently, and the last third strongly curved downward. Its basal portion is 
swollen globularly on the ventral side and hollowed out on the dorsal, thus 
forming an articulation specially adapted to a strong up and down move- 
ment in the vertical plane. The compressed condition of the telsons in our 
material has not permitted a clear view of the section but the keellike 
projections which appear on the lateral view indicate that the spine was 
probably four-sided. The edges of the keels are serrate. 
Appendages. The chelicerae have been seen in position in two speci- 
mens [pl. 32] and one well preserved chelicera has been found detached 
