PLATE XXVIII. 



Echinobrissus expansus Clark (p. 69). 



Acad. Nat. Sci. Philadelphia 1465, type. 



Figure la. Upper surface of the test, 

 lb . Lower surface of the test, 

 lc. Lateral surface of the test. 

 Id. Posterior surface of the test, 

 le. An interambulacral plate, X 3. 



If. Portion of the petaloidal region of the right anterolateral ambulacrum, X 8 

 lg. Apical system, X 5. 



Echinobrissus texanus Clark (p. 70). 



U. S. Nat. Mus. 20266, type. 

 Figure 2a. Upper surface of the test. 

 2b. Lower surface of the test. 

 2c. Lateral surface of the test. 

 2d. Posterior surface of the test. 



2e. Portion of the right anterolateral ambulacrum, X 10. 

 2f. Four interambulacral plates, X 5. 



Trematopygus crucifertjs (Morton) (p. 71). 



Acad. Nat. Sci. Philadelphia 1464, type. 



Figure 3a. Upper surface of the test. 

 3b. Lower surface of the test. 

 3c. Lateral surface of the test. 



