PLATE XVIII. 



PSEUDODIADEMA TEXANUM (RoeniOl) (p. 55). 



U. S. Nat. Mus. 31197. 



Figure la. Upper surface of the test, X 2. 

 lb. Lower surface of the same, X 2. 

 lc. Lateral surface of the same, X 2. 

 Id. Interambulacrum, X 4. 

 le. Ambulacrum, X 4. 

 If. Three interambulacral plates, X 8. 

 lg. Tubercle, X 12. 

 lh. Portion of interambulacrum, X 8. 

 li. Portion of ambulacrum, X 8. 



Heterodiadema ornattjm Clark, n. sp. (p. 56). 

 Johns Hopkins Univ. T 3006, type. 



Figure 2a. Upper surface of the test. 

 2b. Lower surface of the test. 

 2c. Lateral surface of the test. 

 2d. Portion of ambulacrum, X 10. 

 2e. Portion of interambulacrum, X 10. 

 2f. Lateral view of tubercle, X 20. 



