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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 (PI. XVIII, fig. 3 a and c) has the growth-ridges not very prominent; 

 its articular ridge is well-developed, extending downwards more than half the length of the 

 tero-al maro-in. The adductor ridge is always visible, but never prominent. There is no tracé of 

 longitudinal striae on the outer sarface. 



The tero-um (PI. XVIII, fig. 3,^and^) 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 lab rum 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 aré 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 (PI. XVIII, fig. 6) has four nearly equal-sized teeth, the 2 nd and 

 3 rd teeth doublé as usual, and the 4" 1 tooth with a characteristic nob. The 5 th is sometimes short 

 and blunt, and separated from the inferior angle, in other specimens it is quite confluent 

 with that angle. 



The maxilla (PI. 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 nd 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 (PI. 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 



SIBOGA-EXrEDlTIE XXXI //. 25 



