PLATE LV. 



Cidaris mitchelli Emmons (p. 113). 

 Williams College, type. 



Figure la. Upper surface of the test, 

 lb. Lower surface of the test. 

 lc. Lateral surface of the test. 



Cidaris carolinensis Emmons (p. 113). 



Williams College, type. . 

 Figure 2a. Upper surface of the test. 

 2b. Lower surface of the test. 

 2c. Lateral surface of the test. 



Cidaris pratti Clark, n. sp. (p. 114). 



U. S. Nat. Mus. 164663, type. 



Figure 3. Portion of interambulacrum with adjoining ambulacra. 



Cidaris merriami Arnold (p. 114). 



U. S. Nat. Mus. 165438, type. 

 Figure 4. Spine, after Arnold. 

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