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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) 110 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 (PI. XIII, fig. 16). 



Pal pi: 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 (PI. XIII, fig. 16 and 16'). 



Mandible: 5 teeth and the inferior angle; the latter small, bifid. The 2 nd and 3 rd teeth 

 are indistinctly doublé; the distance between the extremities of the 2 nd and 3 rd 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 (PI. XIII, fig. 17). 



Maxilla: The free edge is nearly straight, with a tracé 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 doublé 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 (PI. XIII, fig. 18). 



Outer Maxillae: Outer lobe oval, slightly narrower towards free extremity, inner 

 lnbe 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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