1^2 LOWER PENINSULA. 



and intermingle with those of the adjoining cells. The radial 

 striae are bordered on both sides by a row of circular pores as in 

 the former species. In the centre of the pits the uniting radial 

 crests form a small styliform projection. 



Found in association with the other species in the Niagara group 

 of Drummond's Island and of Point Detour. 



Plate XLVIII. — Fig. 3, silicified specimen from Point Detour, 

 Lake Huron. 



STROMBODES MAMILLATUS, D. Dale Owen. 



Centre of calyces rising from a common interstitial surface as 

 high, mamiform cones, excavated at the top by a crater-like, ra- 

 diated pit. The radial rugae extend over the surface of the cones 

 and across the interstitial surface from one cell into the other, 

 as narrow, equal-sized bands of granulose surface. In the interstices 

 between these bands distant depressions can be noticed, but noth- 

 ing similar to the rows of circular pores bordering the rugae of the 

 other species. The centre of the cell pits is formed by a small 

 styliform projection. General structure as in the other species; 

 composed of alternating layers of well-finished cup membranes, 

 and of strata of vesicles. The size of the mamiform cones and 

 their relative distance differ in various specimens. Width of cell 

 pits from four to five millimeters. Distance from centre to centre 

 from one to two centimeters. Found in the Niagara group of 

 Drummond's Island ; it is also common in the same formation in 

 Iowa, Kentucky, Indiana, etc. 



Plate XLVIII. — Fig. 4, silicified specimen form Point Detour. 



STROMBODES ALPENENSIS, N. Sp. 



Massive horizontal expansions, co\crcd on the lower side by an 

 epithecal crust. Surface formed of shallow calyces, deepening in 

 the centre into a more abrupt pit. The calyces are confluent, or 

 imperfectly defined from each other by tent-shaped, obtuse ridges 



