PLATE L V. 



Upper tier, Lithostrotion mamillare. Subcarboniferous limestone, Wild Fowl \ 



Ba}'-, Michigan. 

 Lithostrotion proliferum, lowest transverse stem. 



Lower tier, single small specimen to the right, Zaphrentis nodulosa. Cornife- 

 rous limestone drift. 

 Group of five specimens to the left of the former, Zaphrentis spinulosa. 

 Subcarboniferous limestone, Bellevue, Michigan. 



