A Michigan Preliminary Section. — Grabau. 185 
Loc. lb. The limestone has here less the character of a 
reef, but appears to have accumulated in the immediate neigh- 
borhood of a reef. It is highly fossiliferous, Favosites and 
Stromatopora being very common, though apparently not form- 
ing very large masses as in the reef portions of the preceding 
localities. Stropheodonta is a well-represented genus, though 
the species are generally small. Gypidnla roiningeri and 
Atrypa reticularis are among the other common brachiopods. 
It has not been ascertained what the actual thickness of the 
limestone is. In the Churchill well twenty-five feet are shown, 
but since these are overlain by drift, it is evident that this is 
merely the minimum thickness and that the actual thickness 
may be somewhat greater. That it is not very much more is in- 
dicated by the nearness of the outcrop of the overlying shales 
on the south. 
Loc. 2. About two miles north of Alpena, at Sta. 11 on 
the section line, a highly fossiliferous kmestone is exposed 
along the roadside and in the adjoining farm lands. This rock 
consists mainly of the stems and joints of crinoids, and of 
various Bryozoa, among which the fenestelloids are the most 
common. In the exposed portions the fossils appear to form a 
loosely agglomerate mass, without the interstitial filling of cal- 
careous sand. Brachiopods are very common, and the space 
between the valves is generally unfilled, except for subsequent- 
ly infiltrated calcite. The brachidium of these brachiopods is 
generally well preserved, indicating a freedom from disturb- 
ances. Gypidula roniingcri and Atrypa reticularis are both 
abundant. Stropheodonta cf. S. deniissa and 6". nacrea are also 
common. Chonetes coronatus is a conspicuous species, while 
Spirifer imicronatus and 5". granulosus are among the other 
characteristic brachipods. 
Fenestella, Loculipora, and the other frondose Bryozoa are 
also well preserved, frequently still showing the original fun- 
nel-like form of the frond. 
Crinoid stems and joints make up the greater portion of 
the mass. These are mostly enlarged, and changed to cleava- 
ble calcite. Dog-tooth spar is common in the cavities, which 
latter are very numerous, since all the remains are loosely 
joined, forming a porous or loose-textured rock. 
No Favosites or other corals have been observed. The con- 
dition of preservation of these fossils is such as to point to 
