ON THE CALCAREOUS DEPOSITS OF STICHOPUS JAPONICUS. 



37 



have an oval disc. Those below 0.06 ram. are comparatively few, at least 

 in the youngest individuals. They all possess a smooth margin. The 

 four pillars of the spire are set very close to one another in the center 

 of the disc! The commonest number of transverse beams are three or 

 four, but exceptionally may become five or two. The pillars often incline 

 towards one another, above the highest transverse beam but one, so 

 that the spire frequently looks as if it were slightly conical or ended in a 

 point. There are minute teeth on the spire, especially near the tip. 

 The height of the spire is generally about 0.06 mm. but may become 

 slightly higher (0.078) or lower (0.048). 



In older individuals of this group — e. g. in those respectively 39, 

 40, 46, 50, 60 mm. long — the tables whose disc is less than 0.06 mm. 

 sometimes becoming as small as 0.03 mm. are mixed with larger ones in a 

 greater proportion than in younger individuals. Many of these discs 

 have only eight holes i. e. four small holes in addition to, and alternating 

 with, the four large holes at the center. Those with only the four 

 central holes (fig. 3) which are such a prominent feature of later stages 

 are as yet very rare, and even these have a tolerable spire. The height 

 of the spire seems also in many cases somewhat reduced, and those with 

 two transverse beams are of much more frequent occurrence. The 

 tables are also much less closely scattered than heretofore. One indi- 

 vidual 70 mm. long I feel justified in placing in this group, for although 

 the features given above for the individuals that are 39-60 mm. long 

 in contrast to younger individuals are brought out still more prominent- 

 ly, nearly all the tables have still some sort of spire, even if the spire 

 has often only one transverse beam, or may consist of only three or two 

 pillars. 



We may therefore conclude that young individuals whose lengths 

 are below about 70 mm. possess calcareous bodies which are all well 

 formed tables. 



It is evident that the specimens which vont Marenzeller examin- 

 ed, belonged to this group, for the largest one in his possession measured 

 70 mm. This circumstance accounts for the fact that he makes no refer- 



