NIAGARA GROUP. 
171 
appears to be oval, and surrounded by a thin calicle. Where worn down, the form ot tiie 
aperture changes, and is more or less tripetalous or irregular. Under an ordinary magnifier the 
cells appear like minute papillose points, with an oval or roundish aperture, and the variety of 
form is scarcely perceptible. 
Fig. 4 a. A fragment of a larger frond. 
Fig. 4 b. A portion of the surface enlarged, showing the papillose cells, and tubercles with 
smooth summits. 
Fig. 4 c. A small portion still further enlarged, showing some variety in the form of the apertures. 
Position and locality . In the shale of the Niagara group at Lockport. 
Genus LICHEN ALIA ( nov. gen .). 
[Gr. Xy/evos, lichen, and aXios, marine .] 
Membranous or subcalcareous bryozoa, growing in circular or flabellate forms, concentrically 
or radiately striate, celluliferous on one surface only ; frond usually a thin membrane, though 
often unequally thickened and contorted or wrinkled. 
This genus includes several species of Bryozoa, which usually occur in circular or expanded 
forms presenting a striated surface. It is only in rare instances that distinct cells are visible, 
though in most cases the surface appears marked as if by stigmata, or the commencement of 
cells, which sometimes rise in low nodes without presenting any defined apertures. Although 
many specimens have been examined, it is still difficult to point out the true relations of these 
forms. The genus is perhaps more nearly like Diastopora or Udotea than any others, but 
it possesses characters entirely peculiar, and is probably a true palaeozoic type. 
567. 1. LICHENALIA CONCENTRICA (». sp.). 
Pl, XL E. Fig. 5 a - g. 
Frond circular, slightly cup-form in the young state, flattened at maturity, and often variously 
contorted from irregular growth or accident, and thickened at intervals; surface concentrically 
marked by fine striae and prominent concentric folds or ridges; celluliferous side less strongly 
striated, cells arranged in concentric lines, almost coincident with the striae ; apertures of cells 
narrow, opening upon the summit of an elevated pustule ; non-celluliferous side of the frond 
showing oval stigmata, produced by the bases of cells on the opposite side. 
This fossil, in its young state, is often found in a tolerably perfect condition ; but in more 
advanced stages, as the size increases, its fragile structure has suffered injury and distortion in 
various ways. The young specimens differ little from the membranous envelope of the base of 
a Chjetetes or Favosites, but they are never found with the structure of these genera. The 
older and larger specimens are usually broken, and in some instances they are folded together 
