PLATE LYI. 
Trematopora (Orthopora) subquadrata. 
Page 177. 
See Plate 55. i 
Fig-. 1. -An enlargement, showing the form and disposition of the cell apertures and the character of the 
interapertural space. (X 18.) 
Hamilton group. Darien Centre, Genesee county, N. Y. 
Fig. 6. An enlargement, showing the cell apertures more broadly oval, and more closely disposed than in 
fig. 1. (X 18.) 
Hamilton group. Near Canandaigua Lake, N. Y. 
Trematopora (Orthopora) iiexagona. 
Page 178. 
See Plate 55. 
Fig. 2. An enlargement, showing the form and disposition of the cell apertures, and the angular inter¬ 
apertural space. (X 18.) 
Hamilton group. Eighteen-mile-cyreek, Erie county, N. Y. 
Trematopora (Orthopora) carinata. 
Page 179. 
See Plate 55. 
Fig. 3. An enlargement, showing the form and disposition of the cell apertures, the alternating nodes, 
and the prominent longitudinal ridges. (X 18.) 
Hamilton group. West Williams, Ontario, Canada. 
Trematopora (Orthopora) ornata. 
Page 184. 
See Plate 55. 
Fig. 4. An enlargement, showing the form and disposition of the cell apertures, and the character of the 
interapertural surface. (X 18.) 
Hamilton group. ' Geneseo, N. Y. 
Trematopora (Orthopora) reticulata. 
Page 179. 
See Plate 55. 
Fig. 5. An enlargement, showing the form and disposition of the cell apertures, and the angular, granu- 
lose and nodose interapertural space. (X 18.) 
Hamilton group. Western New York. 
Acanthoclema sulcatum. 
Page 192. 
See Plate 55. 
Fig. 7. An enlargement, showing the form and disposition of the cell apertures, and the prominent 
angular ridges separating the ranges of apertures. (X 18.) 
Hamilton group. Darien Centre, Genesee county, N. Y. 
Trematopora (Orthopora ?) orbipora. 
Page 188. 
See Plate 55. 
Fig. 8. An enlargement, showing the form and disposition of the cell apertures ; on a portion of.the figure 
the peristomes are obsolete, and the interapertural space elevated and nodose; on the other 
portion the peristomes are moderately strong, and the interapertural space is flat or slightly 
concave. (X 18.) 
Hamilton group. Near Canandaigua Lake, N. Y. 
