S2 LOWER PENINSULA. 



and grow together [into an open, reticulated expansion, or are so 

 densely crowded as to form an uninterrupted basal leaf, from 

 which the tubes singly ascend into a vertical, subparallel position, 

 and then grow up with remarkably straight stems, if not disturbed 

 by accidental impediments. 



The stems in the erect growing parts of the colonies are remote 

 from each other about the width of a tube diameter, or more, and 

 are connected by slender, transverse tubules at intervals of from one 

 half to one centimeter. The tubes are annulated by delicate 

 wrinkles of growth, with periodical, sharper offsets, causing an ar- 

 ticulated appearance. Internal structure longitudinally striate by 

 spinulose crests, and intersected by funnel-shaped, irregular dia- 

 phragms prolongated with the lower apex into long siphons. 



Occurs in the upper Helderberg limestones of Mackinac ; fre- 

 quently also in the drift, associated with corniferous limestone fossils, 

 and in the corniferous limestones of Canada, New York, and of 

 the Falls of the Ohio. 



Plate XXXI., Fig. 2. — The small specimen attached to the lower 

 left-hand corner of the other specimen represents a fragment of a 

 laminar, basal expansion with erect, circular orifices found in the 

 drift. Figs. 3 and 4 are silicified specimens from the Falls of the 

 Ohio — the one with larger sub-flexuose tubes, the other with more 

 slender and straighter tubes. 



SYRINGOPORA MACLUREI, Billings. 



Tubes about three millimeters wide, flexuose, occasionally touch- 

 ing each other, and then diverging again, or at other times of more 

 regular, subparallel growth, with interstitial intervals usually larger 

 than a tube diameter, and with remote, slender, transverse tubules of 

 connection. This coral resembles the former species, differing from 

 it only in having a larger tube size, and a more irregular mode of 

 growth, but in many instances it becomes difficult to decide 

 whether a specimen belongs to one or the other form. 



Plate XXXI. — Fig. i represents a fragment found in the drift of 

 Ann Arbor, exhibiting the terminal portion of a colony. In Fig. 

 2 the large specimen is another drift specimen, seen from the basal 



