PLA TE XI, 



PAGE. 



Pterotockinus bifurcatus. Natural size. Prof. Wetherby's collection, . 136 

 Fig. la. Upper view. 

 16. Basal view. 

 \c. Side view. 

 Pterotocrinus acutus. Natural size. Prof. Wetherby's collection, . 134 



Fig. 2a. Upper view. 

 26. Basal view. 

 2c. Side view. 

 Pterotocrinus spatulatus. Natural size. Prof. Wetherby's collection, . 137 

 Fig. 3a. Upper view. 

 36. Basal view. 

 3c. Side view. 

 FOKBESIOCRINUS PARVUS. Two diameters. Prof. Wetherby's collection, . 138 



Fig. 4a. Azygos. 



46. Opposite side. 



PLATE XII. 



Atactopora multigranosa 122 



Fig. 1. View of specimen grown ui)on an Orthoceras. Natural size. E. O. 

 Ulrich's collection, 

 la. Portion of the surface of same, enlarged to 8 diameters. 



Atactopora maculata, 121 



Fig. 2. Portion of a large specimen. Natural size, E. O. Ulrich's collec- 

 tion. 

 2a. Portion of the surface of same, enlarged to 8 diameters. 

 26. A transverse section, showing the pseudo-septa to be better de- 

 veloped here than at the surface. Magnified to 5 diameters. 

 2c. A longitudinal section, cutting through two of the maculse. En- 

 larged to 5 diameters. 



Atactopora hiesuta, 120 



Fig. 3. A small example attached to an Endoceras. Natural size. E. O. 

 Ulrich's collection. 

 3a. Portion of the surface enlarged to 8 diameters. 

 36. A transverse section enlarged to 5 diameters. 



Atactopora mtjndula, 123 



Fig. 4. A very fine specimen attached to Chcetetes mammulatns. Natural 

 size. E. O. Ulrich's collection. 

 4a. A portion of the surface of same, enlarged to 8 diameters. 



Atactopora tenella, 123 



Fig. 5. A portion of a large specimen that is attached to a frond of C. 

 mammulatus. Natural size. E. O. Ulrich's collection. 

 5a. Portion of same enlarged to 8 diameters, showing distinctly the 

 pseudo-septa. 



Atactopora subramosa, 124 



Fig. 6. An example showing the sub-ramose character of the species. 

 Natural size. E. O. Ulrich's collection. 

 6a. Portion of the surface of same, enlarged to 8 diameters. This fig- 

 ure shows a number of the cell-mouths much contracted by 

 accretions to the margins ; and the great irregularity of the 

 cells as presented at the surface. 



