SPATANGACE.E. 



ECHINIDJE. 



SPATANGACEJE. 



Genus Amphidotus. Agassiz. 



Generic Character. — Body ovate or cordate, convex, having two sets of ambu- 

 lacra, dorsal and oral ; four of the dorsal ambulacra truncate, oblong ; dorsal im- 

 pression within the ambulacra ; sub-anal impression ovato-cordiform, terminal. 



COMMON HEART-URCHIN. 



mermaid's head. 



AmpMdotus cordatus. Pennant. 



Specific Character. — Body cordiform ; a deep dorsal depression ; dorsal depres- 

 sion ovate ; post-oral spinous space broadly ovate. 



Echinus spatagus, Merret, p. 192. Linnjeus, 1104? Borlase, p. 278, 

 t. xxviii. f. 28. Encyc. Mcth. pi. clvi. f. 28. Lister, 

 App. t. i. f. 1 3. 



