402 NEW YORK STATE MUSEUM 
much thickened and produced at an angle into a falcate lobe; and the other 
is marked by a distinct darker band obviously representing a doublure. 
The thickened margin shows different surface sculpturing on the two sur- 
faces that are separated by matrix, and is also due to a doublure. From 
the direction of the droplike surface scales or spines and the form and 
direction of the lobe at the angle, as well as the presence of the doublures 
on the margins, we infer that the fragment is the postlateral portion | 
of a segment. From its angular form we further infer that it belongs 
to a tergite and from the fact that the lateral thickened margin rapidly 
diverges in posterior direction from the main axis, that it was an anterior 
tergite and also that the preabdomen of this species must have rapidly 
expanded, as in Eusarcus. 
The ornamentation is distinctly eurypteroid. It consists of widely 
separated, rather irregularly distributed, blunt or club-shaped spines; 
on the body of the tergite of closely arranged oblong to angular 
interior thickenings of the upper test of the thickened lateral margin, and 
one row of subangular impressed scales, probably originally spines, along the 
posterior margin. The scales of the lateral margin are also impressed on the 
cast of the underside of the integument and consisted of local thickenings. 
The second determinable fragment is the posterior portion of the telson. 
Its detail is well shown in White’s photographs [op. cit. pl. 10, fig. 3, 4]. 
It is acutely hastate in outline and of somewhat complicated structure. 
Our conception of it as obtained from the relievo and intaglio speci- 
mens, is best understood by the diagrammatic transverse section, text 
figure 92. It consists of two separate laminae. One of these is covered 
with the large droplike scales as on the rest of the integument and for this 
reason is considered by us as the dorsallamina. Theotherissmooth. The 
interspace between the two is occupied by rock, as shown by a patch 
clinging to the dorsal side. The dorsal side was of one uninterrupted lamina, 
as is well shown at the proximal end of the intaglio; the ventral side, however, 
consisted of two laminae, separated by a median cleft. This is distinctly 
shown by the proximal and distal ends of the specimen [text fig. 90]; at the 
