CORALS AND BRYOZOA. 
31 
infrequent. Apertures broadly oval, sometimes nearly circular, length .33 
mm., width .25 mm.; irregularly disposed, frequently in contact. Anterior 
margins thin, very slightly elevated; posterior strongly elevated, oblique; 
sometimes with two slight denticulations, which give to the aperture a sub- 
trilobate form. Surface marked by maculae, the centers of which are distant 
from each other about six mm.; the apertures immediately adjacent are larger 
than the others, more oblique and radiating from the maculm. Interaper- 
tural space smooth or vesiculose. Intercellular space vesicular; vesicles 
irregularly arranged, many of them, comparatively, very large. 
The surface of this species presents a variable appearance, according to the 
degree of weathering. 
Formation and localities. In the shaly limestone of the Lower Helderberg 
group, at Catskill, and near Clarksville, N. Y. 
Lichenalia torta. 
PLATE XV, FIGS. 1-5, 7. 
Lichenalia torta, Hall. Thirty-second. Rept. N. Y. State Mas. Nat. Hist., p. 157. 1879. 
In part Lichenalia forf(i,”!lALL. Report of State Geologist for 1SS2. Expl. pi. 15, figs. 1-7. 
Zoarium consisting of lamellate expansions; sometimes flat, at other times more 
or less involved and contorted. Under surface a thin epitheca marked by con¬ 
centric wrinkles and striae, with fine radiating striae. When the celliliferous 
tissue of the bryozoum has been removed, the radiating striae on the upper sur¬ 
face of the epitheca are very sharp and prominent, and at their junction with 
the concentric striae form minute nodes. Cell apertures broadly oval or circu¬ 
lar, sometimes sub-triangular or trilobate, diameter .30 mm.; space between 
adjacent apertures equal to, or less than, the diameter of an aperture. 
Anterior margin slightly elevated, posterior side strongly elevated, with two 
slight denticulations. Surface with slightly elevated monticules, 
Formation and localities. Lower Helderberg group, near Clarksville, and at 
Schoharie, N. Y. 
