PLATE XXXVIII. 



HoLASTKR (SIMPLEX Shumard (page 76). 



Fig. la. Upper surface of tlie test. 



lb. Lower surface of the same. 



Ic. The right antero-lateral ambulacrum, enlarged. 



Id. Portion of the petaloidal region of the same. 



le. Four basal plates of the same. 



If. Apical disk, enlarged. 



Ig. Tubercle, highly magnihed. 

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