71 



portions of the scutum, tergum, upper latus, and infra-median latus have a shape of their own, 

 which can be made out only by separating them from the chininous covering by means e. g. 

 of caustic potash. 



The figure 4 of PI. VI represents this variety and illustrates another peculiarity of the 

 specimens caught by H. M. S. "Siboga"; the four specimens form two couples of two: in the 

 pair figured both specimens are attached to one another and at the same time to the long 

 silicious needles of a sponge; in the other couple the one is attached to the extremity of the 

 peduncle of the other. The shape of the calcareous portions can be distinguished through the 

 chitinous membrane which covers almost the whole surface; very small parts of the scutum near 

 the angle formed by the occludent and tergal margins, and of the tergum near the angle formed 

 by the occludent and carinal margins, remaining uncovered. At these places, where the umbones 

 are, the surface of the valve is quite white and opaque, the chalk being quite amorphous; 

 the rest of the valve appearing blueish, more or less transparent and crystalline. Naturally, this 

 difference can be seen best after isolating and cleaning the calcareous valves (PI. VI, fig. 5). 

 The peduncle of this variety is longer than the capitulum; it is not so long, however, as in the 

 var. robusta. In the four specimens I was able to investigate, the dimensions were as follows: 

 Specimen i. Length of capitulum 477. mm. Length of peduncle 60 mm. Number of rings on 



peduncle ± 48. 

 Specimen 2. Length of capitulum 49 mm. Length of peduncle 60V0 mm- Number of rings on 



peduncle zt 49. 

 Specimen 3. Length of capitulum 45 mm. Length of peduncle 56 mm. Number of rings on 



peduncle ± 40. 

 Specimen 4. Length of capitulum 45 mm. Length of peduncle 48'/,. mm. Number of rings on 

 peduncle =h 48. 



The rings formed by the scales on the surface of the peduncle are not so prominent 

 as in the variety robusta, they are still, however, very conspicuous. The peduncle as a whole 

 is stout and cylindrical — it looks like a piece of rope. 



This variety was collected by H. AI. S. "Siboga" at one Station only, viz.: 



Stat. 74. June 8, 1S99. Lat. 5°3'.5S., Long. ii9°E. Depth 450m. Bottom: Globigerina ooze. 

 Four specimens: two couples of two. 



In the descriptions of Pilsbry and Fischer, details on the structure of the animal's body 

 are wanting. I studied some of the peculiarities with the aid of one of the specimens of Station 74. 



Mouth. Labrum not very bullate with a strongly developed, anteriorly projecting part 

 which is triangular and pointed at the extremity; crest with a few extremely minute triangular 

 teeth. Palpi elongate, about three times as long as broad, densely beset with hairs towards 

 the extremity and along the internal margin. 



Mandibles stout with four teeth and the inferior angle. Between the first and second 

 teeth two much smaller ones are observed, making the number six, if these are also counted. 

 Inferior angle blunt, indistinctly pectinated (PI. VI, fig. 7). 



71 



