Plate XI. 



(All the specimens are in the collection of the Museum of Comparative 

 Zoology at Cambridge. The illustrations are slightly reduced.) 



Page. 

 Figs. 1-5. Clavilithcs conjuuctus. specimens of various ages, showing varie- 

 ties (1067, 27764, 1068 (3) ) 107 



6. Clavilithes dameriacensis, an accelerated individual (27759) loi 



7-9. Clavilithcs parisicnsis. three specimens showing variation (1073).. no 



(17S) 



