CRUSTACEA. 
175 
Hinge-line short, straight; anterior margin curving somewhat abruptly for 
a short distance, thence broadly rounding to the postero-ventral edge, there 
curving abruptly forward and passing in a nearly straight line to the poste¬ 
rior extremity of the hinge. Margins distinctly and sharply elevated on all 
except the dorsal side. 
Nuchal furrow scarcely distinct, cutting off a sub-triangular area on each 
valve, similar in relative proportions to that in E. punctata. 
The Cephalic region occupies about one-fourth the area of each valve, and 
its surface is mostly covered by a single large, elevated node, irregular in 
outline and when uncompressed, merging into one inconspicuous node lying- 
near the dorso-lateral angle, another on the hinge-line at the nuchal furrow, 
and a third just opposite the nodiform termination of the lower thoracic carina. 
The Thoracic region bears two conspicuous nodes, one near the hinge-line, 
apparently continuous with the sharply elevated dorso-lateral margin, the 
other situated mediall}^ abutting closely upon and often apparently con¬ 
tinuous with the lower carina. This carina lies at a little more than one- 
third the width of the valve from the ventral margin, takes its origin at or 
upon the median thoracic node and passes backward in a broad curve, be¬ 
coming extinct considerably within the postero-lateral margin. At a little 
more than one-half the distance between this carina and the hinge-line, 
there is a short, straight, or dorsally curved carinate row of sharp pustules. 
The postero-dorsal margin is also sharply elevated and sub-carinate near 
the hinge. 
The Surface of the carapace is covered with sharp, sub-spiniform pustules on 
its elevated portions, the depressed areas being smooth or minutely punctate. 
Abdomen composed of six somites, which become more elongate in outline 
toward the caudal-plate. Somites sub-cylindrical, bearing three transverse 
rows of posteriorly directed spinules. The first row of these lies just within 
the anterior margin; the second about midway across the segment, and the 
third at the posterior margin. The spinules of the first row are often 
inconspicuous. 
