72 



CIDARIS 



" Table showing variation of form in the spines of Cidaris dav'igera. 



Total 



Ambitus Spine, characteristic of the . ,, . 

 1 !• ,-1 11 /- .1 lenprth of 



general form of the wliole of Ilie 

 spines attached to any individual 

 test of C. clavigera, nat. size 



Almost unif'oimly 

 cylindrical raid 

 slender; very un- 

 usual form of 

 spine. 



1. 



iiii' 



Almost unifornilv 



cvlindrical, bnt 'iiilll 



i ' • • ! ;^ 



not slender; very 



•iili^l 



Sliglillj' tapering ; 

 rare. 



3. 



Pear-sliaped, longi- 

 tudinal section 

 elliptical ; rati er 



rare. 



4. 



Pear-sbaped, longi- 

 tudinal section 

 ovate; rather 



rare. 



longest 



ambitus 



spine. 



Diameter 



of spine at 



neck. 



M 



Diameter 



at greatest 

 thickness. 



Length of 

 neck before 



swelling 

 commences. 



■3 



Form of apex. 



Hemisphe- 

 rical. 



Hemisphe- 

 rical. 



Subacute. 



Subacute. 



Sub-beniisplie- 

 rical. 



Diameter of test 

 at ambitus. 



Uncertain, 

 about I'O 



Uncertain. 



About 'G 



I-l 



1-2 



