PLATE XXIII. 
Trematopora (Ortiiopora) regularis. 
Page 16. 
See Plates 11 and 13. 
Fig. 1. An enlargement of a portion of a specimen showing the cell apertures obscured by the prominent, 
nodose longitudinal ridges. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
Trematopora (Ortiiopora) granilinea, n. sp. 
Fig. 2. An enlargement of a portion of a specimen, showing the form and arrangement of the cell 
apertures, the nodes and granulose striations of the surface. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
Callopora (Callotrypa) heteropora. 
Page 25. _ 
See Plates 11 and 13. 
Fig. 3. An enlargement of a portion of a specimen, showing the form and arrangement of the cell 
apertures and mesopores. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
FISTULIPORA, «p. ? 
See Plate 14. 
Fig. 4. An enlargement of a portion of the surface, showing the form and arrangement of the cell aper¬ 
tures and mesopores. (X 18.) 
Trematopora (Ortiiopora) ovatipora. 
Page 17. 
See Plate 11. 
Fig. 5. An enlargement of a specimen, showing the form and arrangement of the cell apertures, their 
granulose margins, the node at’the base of each aperture and the nodose longitudinal ridges 
separating the ranges of apertures. (X 18.) 
Lower Helderberg group. New Salem, Albany Co., N. Y. 
Callopora (Callotrypa) occulifera. 
Page 27. 
See Plate 13. 
Fig. 6. An enlargement showing the form and arrangement of the cell apertures and mesopores. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
Trematopora (Ortiiopora) parallela. 
Page 19. 
See Plate 11. 
Fig. 7. An enlargement showing the peristomes in contact and a pominent node at each angle. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
Fig. 8. An enlargement showing the longitudinal ranges of apertures separated by nodose ridges. (X 18.) 
Lower Helderberg group. Clarksville, N. Y. 
Trematopora (Orthopora) canaliculata. 
Page 17. 
See Plate 11. 
Fig. 9. An enlargement showing the form and arrangement of the cell apertures. (X 18.) 
Lower Helderburg group. New Salem, Albany Co., N. Y. 
