SYNOPSIS OF GENERA. 
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Odontotrypa, s. g., Hall (Report of State Geologist for 1885, advance sheets. 
Expl. pi. 30. 1886). [Type, Liclienalia alveata, Hall.] 
The manner of growth and interior structure is similar to Lichenalia. The 
oblique trilobate, closely arranged cell apertures, with strongly elevated denti¬ 
culated margins, forming a crescentic projection over the aperture, constitute 
the principal characters of this sub-genus. 
Example: Lichenalia ( Odontotrypa ) alveata, pi. xxx, figs. 24-27. 
Lichenotrypa, Ulrich (Contributions to Am. Paleontology, vol. i, No. 1, p. 
24. 1886). [Type, Lichenotrypa cavernosa, Ulrich.] 
Zoarium consisting of thin lamellate expansions, incrusting other objects. 
In the earlier stages of growth the cell tubes are short and the apertures cir¬ 
cular or oval and the inter-apertural space smooth, as in Lichenalia. In the 
course of more advanced growth the intermediate space is traversed by thin 
walls enclosing the apertures in polygonal areas, forming an irregular net¬ 
work. Inter-cellular space vesiculose. 
Example: Lichenalia ( Lichenotrypa ) longispina* pi. xxv, figs. 11, 12. 
Selenopora, s. g., Hall (Report of State Geologist for 1885, advance sheets. 
Expl. pi. 25. 1886). [Type, Lichenalia circincta, Hall.] 
Zoarium explanate, incrusting. Apertures sub-circular, with an elevated den¬ 
ticulate peristome, and situated within polygonal vestibular areas formed by con¬ 
necting walls which traverse the surface. Interior structure as in Lichenalia. 
Examples: Lichenalia ( Selenopora) circincta, pi. xxv, figs. 13-15. 
Lichenalia ( Selenopora ) complexa, pi. xxxi, figs. 19, 20. 
Glossotrypa, s. g., Hall (Report of State Geologist for 1885. Expl. pi. 31. 
1887). [Type, Lichenalia paliformis, Hall.] 
Zoarium tubular. Cells arising from the epitheca lining the cylindrical 
frond, intersected by narrow projections (semi-diaphragms) from the cell walls, 
extending partially across the cell tube. Apertures paliform. Intercellular 
structure vesiculose. 
Example: Lichenalia {Glossotrypa) paliformis, pi. xxxi, figs. 15-18. 
Phractopora, Hall (Trans. Albany Institute, vol. x, abstract, p. 12. 1881). 
[Type, Lichenalia (Phractopora) cristata, Hall.) 
Zoarium explanate, free or incrusting, frequently contorted, celluliferous on 
one or both faces. Surface elevated at irregular intervals into prominent 
* Published 1881. This species is identical with Lichenotrypa cavernosa, Ulrich. 1886. 
