442 PROF. C, E. BEECHER ON PALHOZOIC [ Aug. 1902, 
Many of the specimens seem to have suffered little or no com- 
pression in the sediments, and therefore the form and ornamentation 
of the separate somites can be accurately determined. One of 
the middle somites is represented in P]. XVIII, figs. 4-6. The dorsal 
side (fig. 4) shows a transverse row of three nodes across the middle, 
with two additional ones on the latera. The posterior edge has five 
nodes occupying a space equal to the three just infront. The ventral 
side (fig. 5) shows an obsolescence of the transverse row, and a 
diminution to three in the number of nodes on the posterior edge. 
An anterior-end view of this somite (fig. 6) is broadly elliptical in 
outline, and has two nodular elevations at the ends of the long 
axis, serving as pivots for the flexing of the somite. The large 
straight abdomen of the individual represented in Pi. XVIT has the 
somites in contact at the latera only, with a slight gaping on 
the dorsum. During life, these spaces were covered by the inter- 
articular membrane. The somites are more uniform in length than 
in E. punctata, Hall, the ultimate abdominal segment being of about 
the same length as the penultimate. ‘here is a gradual shortening 
forward to the proximal segment, which is also without the central 
row of nodes. 
The lobation of the cephalic area differs somewhat, ac- 
cording to the size and preservation of the individuals. A large 
rounded node occupies most of the cephalic area in each valve, and 
carries the pitted optic node on its posterior side. Between this 
large node and the dorsal line there are often, in mature examples, 
three more or less well-developed smaller nodes. One adjacent to 
the nuchal furrow is always present, and is usually quite prominent. 
In some specimens, this node has the appearance of being double. 
Anterior to this, there is generally a smaller node, and a third one 
occupying the anterior dorsal angle. [nan attempt to construe these 
characters in terms of the appendages, the largest cephalic lobe, as 
will be shown presently, would correspond to the mandibles. The 
anterior dorsal node may be taken as representing the first antennal 
segment; the small one just behind, as the second antennal segment; 
while the somewhat larger and occasionally double node next to the 
nuchal furrow may indicate the position of the two maxille. 
The mandibles in this species (Pl. XVIII, fig. 7) are quadrate 
in outline, the oblique side forming a masticatory surface without 
cusps. Several examples show the mandibles protruding in front 
of the carapace, their inner ends being concealed by the valves 
(Pl. XVIII, figs. 1 & 2). From the size and position of the mandibles 
in these and other specimens, it may be inferred that the large 
cephalic lobes represent hollows on the ventral side, in which the 
mandibles were situated. 
The largest carapace observed has a length of 27 millimetres, 
and a width of 17 mm. across one valve. The smallest carapace 
measures 6 millimetres in length. 
This ornate and beautiful species is now quite as well known as 
any Echinocaris, and is a very characteristic representative of the 
genus. 
