LIST OF ILLUSTRATIONS. XI 



Page. 

 Pig. 62. Pachydictya elegans. a, nearly complete zoarium, natiiral size, 

 branching more frequently than usual; 6, enlargement of surface 

 of same, X 18; c, fragment, X 1-5, with young Streptelasma at- 

 tached 139 



63. Pachydictya flabellum. a, fragment, natural size; 6, surface of 



same, enlarged; c, transverse view of branch. (Copied from 

 Eichwald's figure of Stictopora flabellum.) 140 



64. Pachydictya flabellum. a, tangential section, X 20; 6, another 



tangential section, X 20, showing the appearance in the early 

 portion of the mature zone ; c, tangential section of a young exam- 

 ple, X 20, with open mesopores; d, the usual aspect of vertical 

 sections, X 20; e, vertical section, X 20, of young specimen 141 



65. Pachydictya cyclostomoides. Eichwald's view of Micropora cyclo- 



stomoides. a and 6, fragment, natural size, and a portion enlarged . 142 



66. Pachydictya cyclostomoides. a, tangential section, X 20, showing 



the large oval zooecia; 6, vertical section, X 20 142 



67. Pachydictya bifurcata. a and 6, two fragments, X 1.5; c, tangential 



section, X 20; d, portion of a transverse section, X 20, with well- 

 marked median tubuli 143 



68. Pachydictya bifurcata. a to g, Wiman's figures of Rhinidictya bork- 



holmiensis. a to d, four fragments, natural size; e, surface of frag- 

 ment, X 10; /, vertical section, X 10; g, transverse section, X 10; 

 h to j, Eichwald's figures of Stictopora scalpellum; h, fragment, 

 natural size ; i, surface, enlarged ; j, end view of same 144 



69. Coscinium praenuntium. a, tangential section, X 20; b, vertical 



section, X 20 146 



70. Arthrostylus conjunctus. a, lateral view of the central portion of a 



segment, X 18; b, small portion of noncelluliferous side of same, 



X 18. (After Ulrich.) 147 



71. Arthrostylus obliquus. a, side view of portion of a segment, X 18; 



b, noncelluliferous side, X 18, of the upper portion of a segment. 

 (After Ulrich.) 148 



72. Helopora divaricata. a, fragment, natural size, and X 7; 6, portion of 



the same, X 18; c, transverse section, X 18. (After Ulrich.) 150 



73. Arthroclema armatum. a, large segment of the primary series, show- 



ing a sharply defined, articulating socket, natm-al size, and X 18; 

 b, opposite side of another segment of the primary set, X 18; c, a 

 segment of the tertiary series, X 18; d, complete segment of the 

 secondary set, X 18. (After Ulrich.) 151 



74. Sceptropora facula. a, single segment of this fine species, X 18; b, 



vertical section, X 18, through an entire segment; c, transverse 

 section, X 18, cutting the lower end of a segment; d, transverse 

 section, X 18, through the expanded celluliferous portion. (After 

 Ulrich.) 153 



75. Sceptropora francisa. a, group of three segments, natural size; 6, 



the largest segment, X 9; c, basal portion of the same specimen, 

 X 20; d, tangential section, X 20; e and/, vertical and transverse 

 sections, X 20 154 



76. Nematopora delicatula and N. consueta. a, zoarium, natural size, and 



X 18, of Nematopora delicatula; b, transverse section of same. 

 (After Ulrich.) c and d, two fragments, natural size, and X 18, of 

 the Trenton specimens referred by Ulrich to N. delicatula and 

 here renamed N. consueta 155 



