CRUSTACEA. 
179 
the postero-dorsal margin, which is nearly straight. The entire margin is 
elevated and is especially strong upon the posterior portion. 
Nuchal furrow quite conspicuous, directed obliquely forward from the 
hinge-line. 
Cephalic region apparently sub-triangular upon each valve and elevated 
into a conspicuous node, the surface of which is covered with sharp, scat¬ 
tered tubercles. 
Thoracic region characterized by an arrangement of nodes similar to that 
observed in Echinocaris sublcevis: a transverse dorsal node, just behind the 
nuchal furrow, directed slightly forward, followed below by a second trans¬ 
verse, elongated node, produced backward into a faintly curving ridge or 
Carina, which becomes obsolete on the posterior area of the carapace. The 
postero-dorsal area is convex and relatively small. The surface of the thoracic 
nodes and of the postero-dorsal area is covered with conspicuous tubercles, 
while the remainder of the test appears to be minutely punctate or granulose. 
Length of the carapace 13 mm., width 9 mm. 
Abdomen and Post-abdomen not observed. 
Observations. A single valve of the carapace of this species has been observed, 
and, in the disposition of the nodes and ridges upon the surface, it shows a 
close resemblance to its associate in the same formation, Echinocaris sublcEvis. 
E. pusfulosa, however, differs from that species in the less oblique outline of the 
carapace, and the more centrally situated lateral carina. It resembles E. socialis 
in its strongly tubercled surface, but the differences in these two species are 
readily apparent. 
Distribution. In the calcareous concretions of the Erie shales; LeRoy, Lake 
county, Ohio. 
