ECHINODERMS. 

 Analyses of sea urchins. 



23 



SiO., 



{Al,Ve),03 



MgO 



CaO 



SO, 



P.Ov. 



Ipiition 



CO.. needed 



Organic matter, etc 



0.05 



.17 



3.07 



45.87 



.35 



Ti-ace. 



49.47 



98.98 

 39.34 

 10.13 



SiO, 



(AirFeVOj 



MgO..: 



CaO 



SO, 



PoO, 



Ignition 



CO, needed 



Organic matter, etc 



14 



0. 14 



.36 



r>. 23 



44.84 



1.37 



Trace. 



46.70 



98.64 



39.27 



7.43 



Rejecting the very variable organic matter, etc., the reduced analyses assume the following 



form: 



Reduced anali/srs of sm urchiii.i. 



Sea urchins Nos. 8 and 9, Trefocidaris and Heterocentrotus, must be considered separately 

 from the others. No. 9, a giant form, was the subject of four analyses, the shell or test, the 

 dental pyramid, the small white spines on the border of the peristome, and the large purplish- 

 red spine. The large red spine analyzed was 15 centimeters long and weighed 13 grams. 



