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MR. F.J. BELL ON THE ECHINOIDEA. [June 17, 



Measurements of Tripneustes esculentus. 



Measurements of Tripneustes avgulosus. 



EXPLANATION OF PLATE XLIX. 



Dentary Apparatus of Tripneustes. 



Fig. 1 . A pyramid of T. angidosus, showing d, the tooth, c, the epiphysis. 



2. Ditto of T. esculentus. 



3. Ditto of T. depressus. 



1 a. Side view of alveolus of a pyramid of T. angulosus, with e, the epiphy- 

 sis, d, the tooth. 

 2a. Ditto of T. esculentus. 

 3 a. Ditto of T. depressus. 

 lb, 2b, 3b. Eotuke of the three species. 

 1 e, 2c, 3 0. Side view of radii. 

 1 d, 2 d, 3 d. Free terminal portion of the radii. 



1 I add two measurements from Prof. Agassiz for tbe purpose of comparison ; 

 it will be seen that the second set agree very well with my results. 



