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to the basis, and slightly convex. In some specimens the compartments show longitudinal 
and somewhat hyaline stripes; others have indistinct horizontal growth-ridges. 
The scutum (Pl. XVIII, fig. 3 @ and c) has the growth-ridges not very prominent; 
its articular ridge is well-developed, extending downwards more than half the length of the 
tergal margin. The adductor ridge is always visible, but never prominent. There is no trace of 
longitudinal striae on the outer surface. 
The tergum (PI. XVIII, fig. 3,éandd) has the spur short, with the extremity rounded 
or bluntly truncated, standing at less than the length of its free part from the basi-scutal angle; 
the two parts of the basal margin make together a very obtuse angle; the part between the spur 
and the carino-basal angle is rather long; the crests for the depressor muscles are numerous 
and well-developed. 
All the specimens are small: the greatest diameter of the basis of one of the larger 
specimens measures about 4.5 m. 
Concerning the structure of the animal’s body, I can now give several details which 
complete the description given in the Challenger report: 
Mouth. The labrum has a rather shallow notch, the entrance of which is widened, 
and three rather strong and pointed teeth on each side of the notch. Sometimes on one, or on 
both sides, one or even two of the teeth are rudimentary, or wanting — but as a rule three 
teeth are present on each side. 
The palpi are short, broad, and of oval shape. A large part of the outer surface is covered 
by longer hairs, which develop into a tuft of still longer hairs towards the distal extremity. 
Along the upper margin numerous smaller hairs are disposed; short hairs, arranged in a distinct 
row on the inner surface, fall over the edge of the labrum, so long as the palpus is bent downwards. 
The mandible (Pl. XVIII, fig. 6) has four nearly equal-sized teeth, the 224 and 
3"¢ teeth double as usual, and the 4 tooth with a characteristic nob. The 5'* is sometimes short 
and blunt, and separated from the inferior angle, in other specimens it is quite confluent 
with that angle. 
The maxilla (Pl. XVIII, fig. 7 and 7*) has 3 spines situated between: an upper 
pair of the ordinary shape and size, and a lower pair the spines of which are somewhat longer 
than those of the upper pair. The latter two spines and the 3 intermediate ones have, more- 
over, a very characteristic shape, being broad, swollen at the basis, and sharply pointed at 
the extremity. Between the 2™ spine of the upper pair and the first of the three inter- 
mediate ones, a very small interspace represents the notch which in other species is much 
more distinct. 
The outer maxillae (Pl. XVIII, fig. 2) have the outer lobe broadly-oval, with the 
angle at the free extremity rounded. The interior margin is nearly straight. A row of hairs 
runs parallel to the interior margin from the outer to the inner lobe. The latter bears 
the usual feathered hairs and is, moreover, characterised by being prolonged in the direction 
of the basis of the maxilla. 
Cirri. First pair has unequal rami: as a rule the shorter ramus has 6, the longer from 
9 to 11, ordinarily 10 segments. Of the longer, the five basal ones are only indistinctly separated. 
65 
S) 
im 
SIBOGA-EXPEDITIE XXXI14. 
