48 LOWER PENINSULA, 



dition ; identical, but silicified specimens occur in the Hamilton 

 group of Thunder Bay, and in boulders of the drift which inclose 

 other characteristic Hamilton fossils. Entirely similar specimens 

 are found in the corniferous limestone of the Falls of the Ohio, and 

 at Charleston Landing, Indiana. 



Plate XIX. — Fig. i represents a silicified specimen from the drift 

 of Ann Arbor. Fig. 4 is a specimen from the Hamilton group of 

 Widder, C. W., the typical locality for Mr. Billings' specimens. 



CLADOPORA CANADENSIS, N. Sp. 



Palmate, laminar expansions, like the former species, with which 

 it is found associated and agreeing in general structure. Tubes 

 much smaller. Orifices at the ends of the fronds subrotund or trian- 

 gular, with a convex, centrally indented lip on the outer side. On 

 the stouter central and basal parts of the expansions, the lips are 

 appressed, opening, transversal, fissure-like, or the lips have, besides 

 the central indentation, two lateral ones, giving the orifices an arched, 

 semi-lunar form. On the under side of the fronds the orifices are 

 impressed into the massive interstitial wall substance, with a shal- 

 low depressed space surrounding them, which is defined by very 

 obtuse rounded, subpolygonal outlines. On the upper surface, all is 

 raised into stronger relief. Found in the Hamilton group of Wid- 

 der, C. W. 



Plate XIX. — Fig. 3 is a representation of one of these speci- 

 mens. 



CLADOPORA TURGIDA, N. Sp. 



Stout laminar expansions, with orifices on both sides. Tubes 

 thick-walled, with a narrow cylindrical channel, which dilates near 

 the surface into transversely oval or kidney-shaped oblique orifices, 

 spreading, with the inner part of the margins, into a common inter- 

 stitial surface, on which, by slightly raised carinas, the polygonal out- 

 lines of each tube are defined. The outer margin projects as a 

 short lip sinuated on both sides, or simply straight. In well-pre- 

 served specimens, on the expanded part of the orifices, longitudinal 

 furrows are faintly developed, as in the genus Striatopora. A differ- 

 ence is noticeable between the upper and under side of the fronds. 



