24 LOWER PENINSULA. 



FAVOSITES PYRIFORMIS, Hall. 



(ASTROCERIUM, Hall.) 



It grows in globular or pyriform masses, with a narrow, conical 

 basal end, surrounded by an epithecal crust. Tubes rounded- 

 polygonal, unequal in the same specimens, and in different speci- 

 mens varying from one and a half to three millimeters in diameter. 

 Diaphragms flat, moderately close. Tube channels radiated by lon- 

 gitudinal rows of spinules. Pores not very numerous, in a single 

 or double row on each side. Not figured. 



Another species, which I name Favositcs spongilla, is common in 

 the Niagara group at Paul's Station, Indiana. It is likewise of 

 pyriform, conical growth, with subramose excrescences from the 

 discoid upper surface, like some forms of bathing sponges. Tubes 

 small, not over one millimeter wide, with slightly dilating, sub- 

 rotund orifices. Diaphragms convex. Tube cavity surrounded by 

 rows of spinules. Pores not clearly visible in the small silicified 

 specimens, not larger than a walnut. I have not figured the latter 

 two species, as they are not found in Michigan, but have thought 

 it well to mention them as well-marked characteristic forms of the 

 Niagara group. 



FAVOSITES HEMISPHERICUS, Yandell and Shumard. 



Synon., FAVOSITES turbinatus, Billings. 

 Not Fay. hemispil, Milne-Edwards. 



Through misapprehension, Milne-Edwards described, under the 

 name Emmonsia hemispherica, as synonymous with Yandell and 

 Shumard's species, a Favosites entirely different from the speci- 

 mens originally designated by that name. All the original speci- 

 mens of Fav. hemisph. kept in Mr, Yandell's collection are iden- 

 tical with Favositcs turbinatus of Billings. We have to restore, 

 therefore, the name hemisphericus to this species, for which it 

 originally was intended, and give to Milne-Edwards' species the 

 name Favosites Emmonsii, in place of Emmonsia hemispherica, 

 which genus, for reasons mentioned above, can not be accepted 



