92 GEODIA ATAXASTRA. 



frimi which from seven to twenty, very rarely as many as thirty, fairly regularly 

 tlistributcd rays arise radially. The rays are straight or slightly curved, and 

 ajipear as short cylinders, rounded and often somewhat thickened at the end. 

 Indications of the presence of exceedingly small spines have frequently been 

 observed. The rays are, without the centrum, 0.7-2.6 jx long and 0.2-0.8 jx tliick. 

 The total diameter of the aster is 2.6-6, usually 3-4.5 fi. The small strongylo- 

 sphaerasters of var. laiana are very similar. They have a centrum 1-3 fi, a 

 fifth to a tliird of the whole aster, in diameter, and from eleven to nineteen, 

 rarely as few as nine, rays. The rays are, without the centrum, 0.6-1.5 n, rarely 

 as much as 2.5 fi long, and 0.3-0.8 /t thick. The total diameter of the aster is 

 3-6.4, usually 3.4-4.3 [i. 



The ataxasters are more abundant in var. latuna than in var. angiistana. 

 Those of var. angnstana consist of a spherical or irregularly tuberous centrum, 

 1.4-3.5 ft in diameter, from which from one to eight rays arise. The rays are 

 conical or, more frequently, cylindrical and always rounded, sometimes thick- 

 ened at the end. They are rough or distinctly sjiined, without the centrum, 

 0.3-2.8 /i long and 0.4-1.2 /£ thick. This distribution is most irregular, and 

 they arise radially or obliquely. Those of the same aster often differ very con- 

 siderably in size. When only a few, two to four, rays are developed, they 

 usually stand close together and form a bunch arising from one point of the 

 surface of the centrum, the rest of the latter being often rough or spiny, 

 but free from rays. When more rays are present they are usually somewhat 

 scattered, but in this case also a large part, generally more than a half, of the 

 surface of the c(>ntrum is free from rays. The whole aster is 4-7 /( in diameter. 

 The ataxasters of var. latann have from two to fourteen rays. They are very 

 similar to those of var. amjustana, but on the whole larger and covered with 

 somewhat larger spines. Among the ataxasters of this variety a few with 

 branched (bifurcate) rays have been observed. Their dimensions in tliis variety 

 are: centmni 2-4.5 fi, a third to three quarters, of the whole aster, in diam- 

 eter; rays, without the centrum, 0.3-2.5 /i long and 0.7-1.5 fi thick; total 

 diameter 5.3-8.3 /i. 



Strongylosphaerasters w'ith a less pronounced irregularity in the distribu- 

 tion of the rays connect these ataxasters with the small strongylosphaerasters 

 described above. 



The acanlhtylasters occur in both varieties, but they are far from numerous, 

 and particularly scarce in var. angustana. Those of var. angustana have from 

 ten to fifteen rays and measure 8-16 fi in diameter; those of var. latana have 



