28 LOWER PENINSULA. 



each one bears a vertical row of horizontal squama:, which are 

 in alternating position in the adjoining rows. Diaphragms rarely 

 simple, straight, generally compound, of anchyloscd, lateral squamae, 

 presenting an angular, substellate surface ; or the interlacing squamae 

 remain free, and constitute imperfect septa, instead of complete 

 transverse diaphragms. Pores large, forming in single or double, 

 or even triple rows on each side, according to its width, and in 

 places they are much more numerous than in others. It is often 

 noticeable that tubes, for a certain part of their length, are inter- 

 sected by simple, straight diaphragms, without complication by 

 lateral squamae, and again, both above and below, are found 

 divided by very irregularly interlacing compound septa. This form 

 grows in large convex masses, or in discoid expansions, with a con- 

 centrically wrinl^led epitheca on the lower side. Found in the 

 upper Helderberg limestones of Mackinac, and in Monroe County, 

 in calcified condition. Silicified specimens, partly in the shape of 

 casts, are frequently found in the drift. The corniferous limestone 

 of Sandusky, Ohio ; of Port Colborne, Canada ; of the Falls of Ohio ; 

 of Charleston Landing, Indiana, and of a great number of other 

 localities, can be mentioned as abounding in specimens of this coral. 

 Plate VII. — Fig. i is the side-view of a calcified specimen, being a 

 fragment of a larger mass, found at Charleston Landing, Indiana ; 

 lateral pores distinctly visible in the figure. Fig. 2 is a silicified 

 specimen from the drift of Ann Arbor. It shows the inequality in 

 the size of tubes (in some specimens in still greater contrast), by 

 which I was induced to consider these forms as a distinct species 

 (w'^^" " American Journal of Science and Arts," November, 1862, 

 Favos. heliolitiformis), an opinion which I have since changed. 

 Other specimens are found in which the tubes have nearly all an 

 equal size. 



FAVOSITES HAMILTONENSIS, N. Sp. 



Synon., Favosites alpenensis, WinchelL 

 Favosites DUMOSUS, Winchell. 



Tubes rounded-polygonal, unequal in the same specimens and 

 in different specimens, variable from one and a half to two and a 



