294 



COMPARATIVE ANATOMY 



CHAP. 



Fm. 236. — Schizaster lacu- 

 nosus ? from the apical side 

 (original). The spines, and the 

 protuberances on which they 

 stand, are not depicted. 1, The 

 anterior unpaired ainbulacruna ; 



2, thu right anterior ambulacrum ; 



3, fapciole ; 4, the right posterior 

 interanibulacnim ; 5, the right 

 posterior ambulacrum ; 6, the 

 unpaired posterior interanibula- 

 crum ; 7, anal region. 



Fia. 237.— Paleeopneustes 

 Murray! (after Agassiz), 

 from the oral side. 1, The 

 anterior ambulacrum ; 2, 3, 



the anterior right and the 

 posterior right ambulacra ; 

 4, peristome ; 5, anal region. 



