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This description applies to the larger of the two specimens. The smaller specimen, 
which is attached to the side of the larger one, (see fig. 7) no doubt belongs to the same 
form or variety. 
For a study of the body included within the shell I used that of the specimen of the 
variety validus. 
Mouth. Labrum: Crest divided by the notch into two nearly quadrangular parts 
with rounded edges; notch deep, with entrance widened; 3 small and blunt teeth, one of which 
only is distinct, on each side of notch; between the teeth and along the whole crest and 
entrance of notch microscopic hairs are disposed. The thickened sub-triangular shield, the whole 
of which may be considered as the chitinous labrum, terminates interiorly into a distinctly 
rounded off and on both sides broadened manubrium (Pl. XIII, fig. 16). 
Palpi: Shape elongately oval, large, free extremity rounded. Upper margin nearly 
straight, under margin rounded. Internal surface produced to a well-developed crest which runs, when 
the palpi are in a downward position, parallel to the crest of the labrum. The upper margin is 
thickly clothed with short hairs, the under margin is quite hairless. On the external surface 
a conspicuous and very characteristic row of about 10 longer hairs is disposed, the row 
making an angle with the under margin. Towards the free extremity of the palpus this row 
is continued by a few longer hairs disposed along that extremity. For the rest the external 
surface bears a group of longer hairs near the outer extremity only. On the contrary, the 
internal surface bears a dense clothing of short and somewhat curling hairs over a large part of 
the upper half, which are longer along the crest running parallel to the upper margin: these 
latter hairs overhang the crest of the labrum (Pl. XIII, fig. 16 and 16’). 
Mandible: 5 teeth and the inferior angle; the latter small, bifid. The 2"¢ and 3"4 teeth 
are indistinctly double; the distance between the extremities of the 24 and 3"¢ teeth about a 
fourth smaller than that between the extremities of teeth 1 and 2. The lower part of the 
mandible is well-developed; its surface, near the outer edge, is covered with numerous hairs, 
a few of which are seen along the upper margin. The inferior margin, from the extremity to 
more than one half, is covered by a dense row of rather stiff hairs (Pl. XIII, fig. 17). 
Maxilla: The free edge is nearly straight, with a trace only of a notch under the 
upper pair of slightly larger spines. The length of the under large pair of spines slightly 
exceeds that of the upper pair. Number of spines between the upper and lower pair at least 
seven, six of which are disposed in a double row (3 pairs), one standing alone. The upper 
margin is strongly curved, the part near the free edge, however, is straight and runs parallel 
to the under margin. The apodeme is well-developed, its length corresponds to about that 
of the maxilla, measured from the tip of the triangular innermost part to the free extremity 
of the spines disposed along the edge (Pl. XIII, fig. 18). 
Outer Maxillae: Outer lobe oval, slightly narrower towards free extremity, inner 
lobe represented by a semi-circular swelling on the inner and inferior half. The hairs, of which 
the longest are feathered or doubly serrated, as Darwin says, cover a large part of inner 
surface of outer lobe, but they are more densely disposed near the free extremity. A 
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