Plate XIII. 



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

 Zoology at Cambridge. The illustrations are slightly reduced.) 



Page. 



Figs. 1-3. Cosmolithes uniplicatus (1133, 1127, 1133) 142 



4-7. Cosmolithes subuniplicatus (27772, 1124, 27793, 1124) 143 



8, 9, II. Cosmolithes lavigatus (1123) 144 



10. Clavilithes conjunctus, senescent type (1105) 109 



12. Clavilithes cgregius, North German type ( 1 114) 128 



14. Clavilithes deformis ( 1 137) 120 



13. 15^19- Clavilithes scalaris of various ages {2779:6, 27786, 1086, 1083, 



1086, 1088) 117 



(182) 



