PLATE XXI. 
Loa il'i porn ambigua (Hall) (Page 53.) 
Fig. 1. An outline sketch, natural size, illustrating the growth of this species and intro- 
duced for comparison with fig. 2. 
Waldron shale, Waldron, Ind. 
Loculipora ulrichi n. sp. (Page 53.) 
2. Sketch of a zoarium, natural size, showing the narrow elongate basal portion. 
Rochester shale, Grimsby, Ontario. 
Acanihoclema asperum (Hall). (Page 58.) 
[See also PI. XXIV, figs. 7-9; PI. XXV, figs. 17-20.1 
3. Vertical section, X 20, showing the growth of the zocecia from a central line. 
4. Tangential section, X 20, passing through the mature region and illustrating the 
elongate-oval zooecia, solid interspaces, and numerous granular-like acanthopores. 
5. Transverse section, X 20, exhibiting the zocecia radiating from the central axis. 
Rochester shale, Lockport, X. V. 
Clathropora frondosa Hall. (Page 56.) 
[See also PI. XX, Bgs.5 11.] 
b. A vertical section, X 20, illustrating the bifoliate growth, the hemisepta, and 
the general shape <»l" the zocecia. 
7. Tangential section, X 20, with the characteristic wall structure of the genus. 
Rochester shale, Lockport, X. Y. 
Nematopora minuia (Hall). (Page 58.) 
[See also PI. XVIII, fig. 10.] 
8,9. Two tangential sections passing through portions of mature region and exhibiting 
the long, oval zocecia and the numerous small acanthopores 
10. Vertical s ction, X 20. 
11. A portion of fig. 10, X 40, illustrating the acanthopores piercing the interzocecial 
thickening. 
Rochester shale, Grimsby, Ontario. 
Diamesoporn dichotoma Hall. (Page 62.) 
| Seo also PI. XXIV, figs. 28-30.] 
12. A vertical section, X 20, with the opposite sides brought closer together than in the 
specimen. 
13. A tangential section, X 20, passing through both mature and immature regions and 
bringing out especially the shape of the pi unit ive zooecia. 
Rochester shale, Lockport, X. Y. 
Pachydictya crassa (Hall). (Page 57.) 
[See also PI. XVIII, figs. 11,12.] 
14, 15. Vertical and tangential sections, X 20, illustrating the internal structure of the 
Rochester form. 
16. Portion of a transverse section, X 20, introduced to show the mesial tubuli. 
Rochester shale, Lockport, N. Y. 
106 
