36 SIDONOPS ANGULATA. 



DIMENSIONS OF STRONGYLOSPHAERASTERS OF SIDONOPS ANGULATA. 



Number ot fully developed rays 



1-3 



4-9 



10-20 





var. megana, lobose specimen 



24 



23.5 



14-22 . 5 



Total diameter of 



var. megana, massive specimen 



26 



21 



16-24.5 



asters n 



var. microana 







19-24 





Vtll . Ul I'llO 1 1 Icieild. 



24 





17-22 





var. megana, lobose specimen 



12 



12 



8-14 



Diameter of cen- 



var. megana, massive specimen 





lo 





trum /( 



var. microana 







7-13.5 





var. orthotriaena 



11 





8.5-12 



Length of rays 

 (without the cen- 

 trum) n , 



var. megana, lobose specimen 

 var. megana, massive specimen 

 var. microana 

 var. orthotriaena 



8 

 8 



12 



6 



5.5 



2- 7 

 1-6.5 



3- 9 



3.5-5.5 





var. megana, lobose specimen 



4 



4 



2-4 



Basal thickness of 



var megana, massive specimen 



4.5 



4 



2-4 



rays /( 



var. microana 







2-4 





var. orthotriaena 



6 





2-4 



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

 a somewhat rhomboidically distorted outhne (Plate 15, fig. 12). The sterrasters 

 are 85-122 n long, 75-113 n broad, and 57-86 n thick. They are largest in 

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



DIMENSIONS OF STERRASTERS OF SIDONOPS ANGULATA. 





Length 



Breadth 



Thickness 











Var. megana, lobose specimen 



105-122 



90-105 



73-86 



Var. megana, massive specimen 



110-120 



100-114 



70-83 



Var. microana 



85-97 



75-90 



57-65 



Var. orthotriaena 



90-111 



80-94 



65-79 



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 : 89 : 66, 

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



In a thin radial splinter of a very young sterraster of the massive specimen 

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



