56 LOWER PENINSULA. 



lip, while the inner part of the walls forms an undefined, common 

 interstitial surface. The orifices of the stems are of quite different 

 shape ; their tubes diverge from an imaginary axal line in an 

 ascending curve toward the periphery of the stems, opening there 

 in various degrees of obliquity, under crested polygonal outlines 

 which inclose shallow conical pits, at the bottom of which the tube 

 channels open as narrow, transverse, more or less curved fissures, 

 about one millimeter wide in the longer direction, and one quarter 

 of a millimeter in the shorter. The body side of these pits is 

 formed of spreading walls, which help to form the front part of the 

 orifices next above. The outer half of the pits is formed by the 

 obliquely truncated ends of the extremely massive tube walls, and 

 projects under the form of a clumsy lip, giving the stems a very 

 rough appearance. The outer transverse diameter of the orificial 

 pits is nearly two millimeters ; the compressed, band-like tube chan- 

 nels become circular at short distance in from the peripheral ends, 

 and are about one third of a millimeter in width. Pore channels 

 distant. Diaphragms have not been noticed. 



Plate XXII., Lower tier. — Upper third figure from the right 

 side represents a silicified fragment of a reticulated expansion, from 

 the Falls of the Ohio. 



CLADOPORA EXPATIATA, N. Sp. 



Reticulated expansions of cylindrical or compressed palmate 

 stems, of a diameter from one to two centimeters, attached by a 

 massive basal expansion. Tubes of the basal part diverging out- 

 ward, prostrate, and more compressed than those of the stems, 

 with a sharp scaly lip at the outer margin. Tube walls generally 

 very stout. Orifices of the stems variable in the same specimens. 

 Usually they open with no great obliquity to the surface, and join 

 under irregular, polygonal crested outlines inclosing deep conical 

 cell pits, narrowing into cylindrical tube channels. The dilated 

 margins are not converted on the outer side into a lip, but form a 

 uniform network, as in a Favosites. Often also, by incrassation of 

 the tube walls, the cell pits become partly filled, and shallower in 

 the expanded marginal portion, while the crests of their circumfer- 

 ence are rounded off. In other specimens the tubes open with great- 

 er obliquity to the surface, and do not join with crested margins encir- 



