THE GENUS PTERYGOTUS 189: 
shows more or less distinctly the carapace and one of the body 
segments. 
On the larger slab (Plate XV. [Plate 26] fig. 2), the impression 
of the metastoma is distinguishable within the outline of the carapace, 
but it is thrown out of place, so that its long axis is directed 
obliquely forwards and to the right side, at an angle of forty-five 
degrees to that of the body. Close to the anterior extremity of 
the metastoma, but projecting beyond the boundary of the carapace, 
lies the basal joint (¢) of an appendage with articulated, curved, 
pointed and striated, teeth, like those of the endognaths of the 
preceding species. 
The dentated edge of this organ lies almost parallel with the long 
axis of the metastoma; but beyond it, and more towards the middle 
line of the body, there is another curved edge (c’), similarly provided 
with striated and articulated teeth, but cutting the first at a large 
angle. Is this part of a second endognath of the same side, or is it 
that of the other side turned round? In any case the parts are 
thrown far out of their natural position. 
On the left-hand side, between the base of the metastoma and the 
middle of the lateral margin of the carapace, the imperfect impression 
of part of the toothed edge of another appendage (¢’) is dis- 
cernible. It is turned backwards (so that it is certainly displaced), 
and the teeth are somewhat curved and striated. If there are two. 
endognaths on each side, this might well be one of the left pair turned 
round. 
On the left-hand side, the palp (e) of the ectognath is in position, 
but nothing is to be seen of its basal joint. On the right-hand side, 
the large basal joint of an ectognath lies detached and turned round, 
so as to have its cutting edge directed backwards. A confused mass 
occupies the place of its palp. 
Where the antenne should be there is, on the left side, a long and 
broad dark impression (4) fading away externally. On the right side 
there is a somewhat similar marking which continues the line of 
that on the left hand, but is very broken and irregular. However, 
it divides distally into two branches, on the opposed edges of which 
the remains of the characteristic antennary teeth can readily be 
discovered (0’). 
Whether these impressions represent one antenna, or portions of 
both, I cannot say, but between them, and in front of them, a dark 
sculptured area (/) presents itself, which is cut off anteriorly by the 
fractured edge of the stone. On the right side, this area is bounded 
by a well-defined margin, which runs between the posterior boundary 
