24 LOWER PENINSULA. 



species. Spinules in twelve distinct longitudinal rows. Diaphragms 

 flat, or gently convex, closely approximated. Pores in one, rarely 

 in two rows on each side. 



Grows in large, massive expansions, with an epitheca on the lower 

 side. 



Found abundantly in the Niagara group of Michigan, and loose 

 in the drift ; it likewise occurs in the Niagara strata of Iowa, In- 

 diana, Kentucky, and New York. 



Plate V. — Fig. 3 is a silicified specimen from Drummond's Island. 



FAVOSITES OBLIQUUS, N. Sp. 



Tubes polygonal, compressed, like an Alveolites, and opening 

 obliquely to the surface. Large diameter of tubes, three millimeters ; 

 small diameter variable according to the degree of compression. 

 In rare instances the tubes are not compressed, or only slightly so, 

 and open rectangularly to the surface. The inner circumference 

 of the tube walls is striate^ by twelve longitudinal furrows with in- 

 termediate band-like spaces, each of which bears several longitu- 

 dinal rows of spinules. Diaphragms subplane, with from eight to 

 twelve marginal depressions, which, together with the longitudinal 

 furrows and spinulose interstices, give the orifices a very decora- 

 tive, stelliform aspect. The surface of the diaphragms is covered 

 with delicate spinules, like the rest of the inner surface of the tubes. 

 Lateral pores form a single row on each side, wherein it differs from 

 Alveolites, which has larger pores, confined to the two lateral edges, 

 or to their vicinity. 



Large, undose expansions, with an epithecal crust on the lower 

 side. Common in the Niagara group of Drummond's Island and 

 Point Detour ; also found in the drift of the Lower Peninsula ; 

 occurs likewise near Masonville, Iowa. 



Plate XXVIII. — Fig. 2, silicified specimen from Point Detour. 

 The Niagara group of New York and Indiana contains a few 

 other species of Favosites, which are not found in the formation 

 of Michigan; these are : 



