20 LOWER PENINSULA. 



majority of the Devonian forms, instead of longitudinal rows of 

 teretiform spinules, have rows of horizontal squamulae, which, as 

 already mentioned, sometimes coalesce into transverse compound 

 laminae, taking the place of the regular diaphragms, which case 

 never occurs in a Niagara species. 



FAVOSITES FAVOSUS, Goldfuss. 



Synon., Calamopora favosa, Goldfuss. 

 Favosites Niagarensis, Hall, in part. 



Tubes polygonal, of uniform size in the same specimens, but 

 in different specimens variable, from a diameter of six milli- 

 meters to that of two. Internal circumference of tubes longi- 

 tudinally striate by twelve furrows, with intermediate, broader, 

 band-like spaces, which are crowded with slender spinulose pro- 

 jections, either in irregularly dispersed position, or arranged in 

 longitudinal or transverse undulating rows, in accordance with 

 the undose, transverse wrinkles of growth visible on the out- 

 side of the well-preserved tube walls. Diaphragms convex or 

 flat, or even deeply concave, closely approximated or wide apart. 

 All these variations of structure are sometimes observable in one 

 and the same specimen, but usually the different variations of 

 form mentioned are represented by different specimens. The dia- 

 phragms are marked with concentric wrinkles of growth parallel 

 with the polygonal outlines of the tubes, and their entire surface is 

 ornamented by delicate granules or spinules similar to those pro- 

 jecting from the side walls of the tubes. The margins of the dia- 

 phragms at their junction with the side walls are deflected into 

 ;siphon-like depressions, frequently twelve in number, and coinciding 

 with the twelve longitudinal furrows. In many specimens only 

 five or six such siphonal depressions are developed, while in the cir- 

 cumference of some of the very large tubes I counted twenty. 

 These latter are exceptions. In certain specimens the diaphragms 

 connect with the side walls without any perceptible depression. 



Lateral pores connecting the tubes, of moderate size, surrounded 

 by a raised rim, forming on each side of the polygonal tubes, 

 according to its width, a single, or double, or triple row. The pores 



