EXPLANATION OF PLATE XVIII. 

 (All figures after Clark.) 



LINTHIA TUMIDUI.A Clark, p. 304 



1-4. Dorsal, ventral, lateral and posterior views of a complete 

 individual. 



5. Upper portion of the anterior ambulacrum, enlarged. 



6. Several plates from the petaloid region of the left postero- 



lateral ambulacrum, highly magnified. 



7. Apical disk, enlarged. 



8-9. Two views of a tubercle, from the side and from above. 

 Vincentown limesand. 



916 



