209 



The ter gum (PI. XX, fig. iS, b and d, fig. 1 8*) has a rather broad spur, the anterior 

 margin of which is separated from the basi-scutal angle by a minute part of the basal margin ; 

 in other specimens it is confluent with the scutal margin. The remaining larger part of the basal 

 margin is distinctly hollowed out. The scutal margin is nearly straight, the carinal margin not very 

 long. These two margins meet at the apex, which is produced into a sharp spine-like beak. This spine- 

 like beak, however, is a yellowish chitinous structure that is kept in its place by means of the chitinous 

 membrane covering the whole valve. If the valve is boiled with caustic potash this chitinous beak 

 separates from the calcareous valve. (I suppose this is the structure meant by Borradaile when 

 he says that (at the tergum) an apical tooth is present, but broken in the specimen). 



Nothing was known hitherto about the structure of the animal's body, and I think it 

 will be useful to give the following description : 



Mouth. Labrum (PI. XXI, fig. i): notch rather deep, wide at entrance; lateral margins 

 making together an angle, say of 135 , hence the thickened portion of the labrum, which in 

 most species is sub-triangular, is in this species rhombiform, with its height only slightly shorter 

 than its breadth. On each side of the notch three small teeth are seen, of which in one 

 specimen, however, only two were developed; very short hairs are disposed along entrance of 

 notch and between the teeth. 



Pal pi: oval, slightly recurved towards free extremity. Distal part a little narrower, but 

 not pointed. Upper margin almost straight, slightly hollowed out ; inferior margin convex. Hairs 

 scattered over large part of outer surface, forming with some of those along upper margin a not 

 very conspicuous tuft at the extremity. On inner surface numerous shorter hairs form a longi- 

 tudinal group that is disposed at some distance from the upper margin and parallel to it. 



Mandible (PI. XX, fig. 19): extremities of teeth 1 and 2 a trifle farther distant from 

 each other than 2 and 3. Tooth 2 doublé, 3 swollen, 4 small and triangular, 5 confluent with 

 inferior angle, forming together a series of very small nobs. Inferior part only slightly developed. 

 Surface with isolated hairs, and also with some hairs arranged in groups; shorter hairs and 

 spine-like nobs on surface of inferior part. 



Maxilla (PI. XXI, fig. 2): edge long and almost absolutely straight; two spines near 

 upper, two near inferior extremity of edge, the latter a trifle longer than the first. Between the 

 two pairs, 7 spines are disposed. Hairs on surface are seen only near outer edge, those on 

 superior margin as well as those along inferior margin very few only — 6 to 8. 



Outer maxillae (PI. XXI, fig. 3): outer lobe rather broad and not pointed towards 

 extremity. Inner margin almost straight, outer margin rounded. Hairs scattered over inner 

 surface perhaps not quite so numerous as in other species, a group, not a single row, descends 

 from the outer to the inner lobe. Inner lobe elongate, furnished with numerous and partly very 

 long and recurved hairs, the extremities of which are directed inwards and downwards. 



Cirri. First pair has very unequal rami of 6 and 14 segments. Hairs at extremity 

 of 6 th segment of shorter ramus spine-like, slightly curved, strong and feathered. 



Second pair has slightly unequal rami of 7 and 8 segments; shape of segments 

 quadrate; last segments of both rami bear curved spine-like hairs on the extremity, much 

 resembling those of the last segment of the shorter ramus of the i st cirrus. 



81 



SXBOGA-EXPEDITIE XXXI b. 27 



