162 NEW YORK STATE MUSEUM 
Description. Body of small size, ovate-lanceolate in form, four times 
as long as wide, relatively wide in front and broadest at one third of its 
length; moderately convex. 
Cephalothorax relatively small. The carapace occupies one sixth or 
less of the total length of the body, is typically trapezoidal in outline, length 
to width as 3:4 or more frequently as 4:5; its lateral margins nearly 
straight, shghtly converging forward, forming an obtuse, slightly rounded 
angle, with the nearly straight frontal margin.. The posterior margin is 
broadly concave, the postlateral angles truncated, the truncated portion | 
forming a distinct angle with the extremities of the concave part. The 
surface is moderately convex, highest in the middle near the posterior 
margin, where it is about one fourth as high as long. The carapace is 
bordered by a steeply inclined smooth marginal rim, broadest in front and 
narrowing toward the postlateral angles. The outer edge of the carapace 
is sharp; its underside is formed by the narrow doublure to which the con- 
necting membrane is attached. The latter is frequently cleft along the 
anterior median line. Its width and natural position are shown in plates 5 
and 6, figure 2. The compound eyes are situated a little in front of 
the middle, twice as far apart as distant from the lateral margin, one 
fifth, or less, as long as the carapace, bean-shaped, prominent, the kidney- 
shaped visual area entirely smooth. The two ocelli are situated on sep- 
arate tubercles in a line connecting the centers of the compound eyes. 
Along the posterior half of the middle line a broad flat ridge (glabella) 
is delimited by two parallel furrows. Another pair of broader and deeper 
furrows passes in front and outside of the lateral eyes. These can be 
traced to the posterior margin, toward which they converge and become 
fainter. The part of the carapace outside of this furrow is very smooth. 
Frequently a small triangular area ora median furrow is observed on the 
mediofrontal part of the carapace. 
The preabdomen occupies one fourth of the length of the body, and 
is a little wider than long. It attains its greatest width at about the fourth 
tergite. In the best preserved specimens it is almost evenly convex 
