REPOKT ON THE NUEIBK AN CHI AT A. 
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muscles (fig. 2) pass forwards from the posterior part of the upper surface, and are attached 
to the labial disk. The labial disk is of oval form, about 2 cm. long (fig. 2, a, 3, a); 
each of the twm halves of which it is composed measures about 7 mm. in diameter ; it 
is whitish in colour ; the inner edge is irregularly wrinkled ; the mouth is a perpendicular 
slit, with bluish-black walls. — The upper commissure of the mouth having been divided 
in the middle fine as far as the mandibles (fig. 6), the length of that portion of the 
bulbus lying in front of the mandibles was 2 cm. It was lined by a very thick 
(4'5 mm.) cuticle (fig. 6, b), which presented the usual finely striated and stratified 
structure, and was blackish in colour at the outside and at its somewhat attenuated fore- 
end passed into reddish-brown on the inside. The cuticle is firmly fixed along a part of 
the anterior end of the mandibles, over which it passes, to become continuous with the 
cuticle lining the deeper part of the buccal cavity, w T here it is again firmly fixed to the 
mandibles in the region corresponding to the insertion on the foreside (fig. 6). These 
mandibles appear with their free part, yellow-green in colour, at the bottom of the 
above-mentioned anterior part of the buccal cavity ; the right mandible overlaps the left, a 
small portion only of which was therefore visible (fig. 4). On removing the cuticle from 
the strong muscular mass, the inner surface of the latter was visible, traversed by a series 
of longitudinal folds (which correspond to furrows on the cuticle). The muscular mass 
increases in thickness posteriorly ; the flattened, concave, whitish, hinder extremity 
resting on the foreside of the mandibles; the diameter of this part was 13-14 mm. 
The mass is made up of an external circular and an internal longitudinal layer. — The 
mandibles are very large, about 4 '4 cm. long by 2 ‘8 cm. broad and l - 4 cm. high. The 
greater part is concealed within the bulbus, and is of an opaque, milky-yellow appear- 
ance, whitish in front and more yellow behind. The free portion is yellowish-green, 
darker on the backside, and covered with very fine radial striae. In shape the mandibles 
are oval (figs. 4, 5), with an angle at the middle of the internal margin ; the thickness 
(at the middle) is about 3 mm., gradually thinning towards the margins, and eventually 
being only *4-'3 mm. in thickness. The upper and lower ends are rounded ; the external 
margin is convex and thin, the internal straighter and rather thicker ; about the middle 
it gives off a rounded tooth (fig. 5) ; the surfaces are smooth and finely striated concen- 
trically and radially. On the lower part of each mandible is a thickened portion, forming 
a tubercle on both sides (fig. 5). The mandibles are not united by a hinge, although there 
exists a rudiment of this in the shape of a thickening on the upper part of the internal 
margin, but by the cuticle already mentioned which passes from one mandible to the 
other (fig. 4). Both sides of the enclosed portion of the mandibles are covered by a 
thick epithelium of thin cylindrical cells measuring '08 mm. When the epithelium is 
removed, the colour of the mandibles is seen to be a fine canary-yellow, contrasting with 
the greenish colour of the free portion (of a breadth amounting to 10-12 mm.). The 
masticatory edge was worn, but did not appear ever to have possessed denticulations. — 
(ZOOL. CHALL. EXP. — PART XXVI. — 1884.) Cc 15 
