LIST OF ILLUSTRATION'S. XV 



Page. 

 Fig. 126. Nicholsonella gibbosa. a and &, top views of two irregular zoaria, 

 natural size; c, side view of a third specimen of more regular form; 

 d, an example with low monticules, viewed from above; e, tan- 

 gential section, X 20, through a macula; /, portion of the same 

 section, X 20, cutting the ordinary zooecia; g^, several zooecia, X 40, 

 illustrating the minute structure; ^., vertical section, X 8; i, portion 

 of tlie same section, X 20 225 



127. Dianulitesfastigiatus. a, side viewof azoarium, showing the epitheca; 



h, top or celluliferous surface, enlarged; c, edge view of a broken 

 fragment, enlarged, illustrating the uneven fracture; d, the type- 

 specimen of Dianulites detritus Eichwald, natural size. (After 

 Eichwald.) 230 



128. Dianulites fastigiatus. a, vertical section, X 9; h, part of the same 



section, X 20, showing the wall structure; c, tangential section, 



X 20; d, another part of the same section, X 40 231 



129. Dianulites petropolitana. a, tangential section, X 20; b, vertical 



section, X 8; c, several tubes of the same, X 20 233 



130. Dianulites petropolitana. a, tangential section of the form "hexa- 



porites," X 20; 6, small portion of the same, X 35; c, several 

 zooecia of a tangential section, X 35; d, vertical section, X 8, 

 passing through a macula 234 



131. Dianulites petropolitana. a and h, side and basal views; c and d, 



tangential section, X 20, and wall structure of same much en- 

 larged; e and/, vertical section, X 9 and X 20 235 



132. Dianulites petropolitana. IThich's views of Monotrypa (Chaetetes) 



cumulata, a and c, tangential section, X 9, and a small portion, 



X 35, showing wall structure; 6, vertical section, X 9 236 



133. Dianulites grandis. a, the type-specimen, two-thirds natural size, in 



side view; &, view showing simplicity of structure seen in the 

 ordinary tangential section, X 8; c, portion of the same, X 20; 



d, tabulation in vertical section, X 8, cutting four layers of zooecia; 



e, several tubes of a single layer, X 20 238 



134. Dianulites coUifera. a and h, type-specimen, natural size; c, sur- 



face, X 9; d, the usual aspect presented in tangential sections, 

 X 20; e, vertical section of several tubes, X 20; /, a zooecium, 

 X 35, in a tangential section 239 



135. Bythopora subgracilis. a, an ordinary fragment, natural size; h, 



surface of specimen, X 9; c, tangential section of a poorly preserved 

 fragment, X 18; (?, vertical section, X 18. (After Ulrich.) 241 



136. Bythopora subgracilis. a and h, tangential and vertical sections, 



X 20, of a well-preserved Russian example 241 



137. Eridotrypa sedilis. Copies of Eichwald's figures of Cladopora sedilis. 



a and c, two fragments of the natural size; 6 and d, enlargements of 



the same specimens 243 



138. Eridotrypa eedilis. Copies of Ulrich's figures of Eridotrypa mutabilis. 



a, specimen of average size; h, surface of another example, X 18; 

 c, tangential sections, X 18; rf, a zooecium of the same section, X 50; 

 e, vertical section, X 18 244 



139. Eridotrypa sedilis minor. Copied from Ulrich's figures of Eridotrypa 



mutabilis minor, a, b, and c, three average fragments; d, surface 

 of a fragment, X 9; e, tangential section, X 18; /, vertical section, 

 X 18 245 



140. Eridotrypa exigua. a, group of fragments, natural size; b and c, two 



of them, X 9 246 



