in of the
overlapping scuta abuts: here this ridge, instead of projecting straight
out, is oblique or folded over, and thus forms a furrow, receiving the
margin of the scuta. The interior growing surface of the tergum (fig. 1
_b'_, _c_), presents so irregular a figure, that it can hardly be
described; in area it quite equals the scuta; it is slightly concave; at
the upper point of the carinal margin, there is a large, rounded,
protuberant, roughened knob, which corresponds with a small knob on each
side of the inner face of the carina; these knobs seem firmly united
together by membrane. The scutal margin of the terga, in the upper part,
forms a shoulder, largely projecting over the scuta; on its lower part,
there is a small roughened projection. The occludent margin is arched
and protuberant, with a slight fold above the knob on the carinal
margin, just mentioned: this fold is caused by the protuberance of the
central internal ridge of the carina, but is so small, that when the
capitulum is seen from vertically above, it can hardly be distinguished.
Finally, the basal half of the carinal margin, runs in the same line
with the basal margin of the scuta.

_Carina_, moderately large; seen externally, the surface presents an
elongated triangle, with the apex truncated; on the internal face (fig.
1 _b'_, _d_) of the free part, there is (instead of being concave as is
usual) a great central ridge, which projects between the diverging
apices of the terga, as may be seen from vertically above; hence the
thickness of the upper part of the carina, in a longitudinal plane,
almost equals its breadth. The edge of this ridge is rounded. The inner
or growing surface of the carina is tinted purple, and lies in a plane,
oblique to the longer axis of the valve; it is triangular, with the apex
cut off, and the basal margin rounded and protuberant; it is not
concave. There is a central raised line or slight ridge on this inner
surface, and on each side in the upper part there is a small, white,
roughened knob, corresponding with the similar knobs on the carinal
margins of the terga.

_Rostrum_ (fig. 1 _b'_, _a_), rudimentary; in one specimen it was about
1/50th of an inch in width; it is either as wide, or only half as wide,
as the subjacent scale on the peduncle.

_Latera_, rudimentary, placed between the edges of the carina and the
terga; rather smaller than the rostrum; almost cylindrical, slightly
flattened, enlarged at each zone o