34 LOWER PENINSULA. 



FAVOSITES PLACENTA, N. Sp. 



Tubes less than one millimeter wide, rounded-polygonal, sub- 

 equal or unequal, larger tubes and smaller tubes clustered to- 

 gether in separate spots, or single circular tubes dispersed between 

 smaller subangular tubes, as in Favos. Canadensis. Diaphragms 

 partially straight, simple, partially complicated, with lateral hori- 

 zontal squamae. Pores large, distant, in a single row on each 

 side. Grows in discoid, undose expansions, with a concentric- 

 ally wrinkled epitheca covering the lower side. Transition forms, 

 of digitato-ramose form, connect this species most intimately with 

 the former species, Fav. nitella. The specimens with single cir- 

 cular tubes dispersed through the mass of smaller subangular 

 ones show a close affinity to Favosites Canadensis. Although 

 specimens from different localities exhibit numerous minor va- 

 riations, I consider this a well-marked species characteristic of 

 the Hamilton group, from its base to the highest beds. It 

 occurs in the upper strata of Partridge Point, in Thunder Bay, in 

 the next lower strata of Stony Point, in the massive limestones 

 forming the nucleus of the hillocks at Phelps' quarries, and at 

 Broadwell's and Trowbridge's mills on Thunder Bay River. In the 

 outcrops of Little Traverse Bay it is a frequently seen form ; the 

 drift deposits of the Lower Peninsula likewise contain many speci- 

 mens. The Hamilton strata of Bosanquet township in Canada 

 contain it in particularly regular, discoid specimens, which caused 

 me to name it Placenta. Similar forms are common in the Hamil- 

 ton group of New York. 



Plate XL — Fig. i represents small specimens from Widder, C. W., 

 one presenting the upper surface with subequal tubes, the other the 

 under side covered by an epithecal crust. Fig. 2 gives specimens 

 from the same locality, with unequal tubes, approaching in structure 

 Fav. Canadensis. Fig. 3 is part of a large expansion from the 

 Hamilton strata at Broadwell's mill, on Thunder Bay River. 



FAVOSITES RADICIFORMIS, N. Sp. 



Cylindrical and apparently procumbent creeping stems of vari- 

 able thickness, from the diameter of a finger to that of a man's 

 wrist, and often several feet in length, with anastomosing or strad- 



