3G SIDOXOrs AXGULATA. 



DIMENSIONS OF STRONGYLO.^rH.\ER.\STERS OF SIDONOPS .\NGULATA. 



orthotriaena, however, a good many sterrasters have, when seen in this position, 

 a somewhat rhomboitlieally distorted outline (Plate 15, fig. 12). The sterrasters 

 are 85-122 /< long, 75-113 ,« broad, and 57-86 /( thick. They are largest in 

 var. megana, smaller in var. orthotriaena, and still smaller in var. microana. 



DIMENSIONS OF STERRASTERS OF SIDONOPS ANOULATA. 



The average proportion of length to breadth to thickness is in the sterrasters 

 of the lobose specimen of var. megana 100 : 87 : 68, in those of the massive 

 specimen of var. megana 100 :92 :63, in those of var. microana 100 :S9 :66, 

 and in those of var. orthotriaena 100 :88:73. 



In a tliin radial sjjlinter of a very j'oung sterraster of the massive specimen 

 of var. megana with long, slender, and pointed ray-ends, which lay opportunely 



