PALAEONTOLOGY OF NEW-YORK. 
The posterior lateral angles of the joints, from the sixth to the tenth, 
are usually salient, and projecting backwards in a spiniforin process. The 
three first pairs of feet are similar in form, consisting of broad strong 
joints; the angles of the more extreme joints (and perhaps of all) fur¬ 
nished with smooth spines, usually on one side, while the two preceding 
the last one are furnished with a spiniferous process on each distal angle ; 
the last joint being a simple smooth chelate tip. Each pair in succession 
is a little longer than the preceding, and the third pair proportionally 
longer than the second. The fourth pair is more slender, but strongly 
jointed; fully once and a half as long as the third : the last joint is a 
long smooth slender chela, and each of the distal angles of the penulti¬ 
mate joint is furnished with a slender chelate tip, while the other joints 
of the same have shown no such processes. 
The swimming feet are strongly articulated to broad rhoinboidal ma¬ 
xillary plates : the anterior distal angles of the [third], fourth, fifth and 
sixth joints are acutely angular, and project over the next joint in ad¬ 
vance ; the first joint is broadly dilated, and the penultimate is ovate and 
shorter than its preceding. The two joints forming the pincers are nearly 
as long as the five preceding joints, including the maxillary plate. The 
terminal palette is very minute, and, inserted into the notch at the 
extremity, scarcely extends beyond it. The anterior edges of these joints, 
sometimes show serratures. 
The post-oral plate is ovato-cordiform : crust thin, often finely wrin¬ 
kled or striated, and both the dorsal and ventral sides of the thorax and 
abdomen are marked by the peculiar scaly surface. On the dorsal side 
these scale-like processes become developed into spiniform pustules, 
arranged in longitudinal rows down the back; there being usually four, 
and rarely five or six rows visible on the thoracic segments, while the 
abdominal segments preserve but two such rows. This feature is not 
always visible, and the scales of the intervening parts are sometimes so 
prominent as to interrupt the visible continuity of the lines. 
The greater number of specimens examined are imperfect, and but a 
single specimen has shown the limbs entire. 
