72 



CIDARIS 



" Table showing variation of form in the spines of Cidaris davigera. 



Ambitus Spine, characteristic of the 

 general form of the whole of the 

 spines attached to any individua 

 test of C. clavigcra, nat. size. 



Almost uniformly 

 cylindrical ,ind 

 slender; very un- 

 usual form of 

 spine. 



1. 



Total 



length of Diameter 

 longest I of spine at 



ambitus | neck, 

 spine. I 



Almost unifor!(ily 

 cylindrical, but 

 not slender; very 

 rare. 



2. 



Slightly taperiu 



Pcar-sliapcd, longi- 

 tudinal section 

 elliptical ; rati er 

 rare. 



Pear-shaped, longi- 

 tudinal section 

 ovate ; 1 allier 



rare. 



5. 



II 



1-2 



Diameter 

 at greatest 

 thickness. 



Length of 

 neck before 



swelling 

 commences. 



Form of apex. 



Hemisphe- 

 rical. 



Hemisphe- 

 rical. 



Subacute. 



Diameter of test 



Subacute. 



at ambitus. 



Uncertain, 

 about 1-0 



Uncertain. 



Sub-hemisphe- 

 rical. 



About "C 



1-1 



1-2 



.Kujidiiiii 'mU oJjiO/ilti: n:>:)(! ;*'/(;;! bjjov/ 



