-7s 77/e American deohnjist. NOvcmbiT. ii>95- 
in thickness, ol'ten having tiiin hiyers of chert intercala- 
ted, and making up as much as one-third of the mass. Fossils 
appear to be entirely wanting. Above about twenty feet of 
this rock there are usually two or three la^^ers of heavily bed- 
ded dolomite, soft, porous, brownish yellow, with imbedded 
<'hert nodules; then more thin bedded layers of a whit^ or 
light gray color, with scattered nodules of chert. This basal 
member is from 30 to 50 feet in thickness and can pro]>ably 
be recognized only by its stratigra])liical and lithological 
characteristics. 
The second member may for the present be called the lower 
Coralline beds. The rock is at the base softer, more vesicular, 
darker butf. scarcely crystalline, heavily bedded and contains 
LijelUa (iliihra Owen, /J(i///s/tes rafeinildhi Linn.. Sjin'iHioiiora 
verficelhifa Goldfuss, and species of F<troslf<'s, with jierhaps a 
few other corals. Toward the iipper part the layers usually be- 
come thinner, harder and more compact, and considerable chert 
is found. These lower Coralline beds are usually 25 to 
80 feet in thickness. These two lower mem])ers are useless 
for lime or ])uilding stone, except for bridge piers, mill dams 
and footing rock, though they furnish good road materials. 
The next higher member is what has long])een known as the 
Pentamerus beds. These are from 70 to SO feet in thick- 
ness. The texture at the base is like that of the top of the 
lower Coralline, the rock being grayish in color, compact and 
hard, with splintery fracture. Toward the middle the matrix 
becomes much softer, a brighter yellow, scarcely crystalline, 
quite free from chert and very vesicular. The characteristic 
fossil, l^eiitamenis obloiujHs Sowerby, is not abundant at the 
base and is of rather small size. Toward the middle the indi- 
viduals are generall}^ larger and often almost the whole mass 
is made up of this fossil. Toward the top this species becomes 
smaller and is comparatively rare, and is accomjianied in 
places by Pcnfaniei'Ks pei'fiihhiisns Hall and Whittield. These 
beds also contain Cerionltes ddcfjiltoidrs Owew, llnhislfes cote- 
inddfiis Linn., Alrmxi reficnhi ris Linn.. Atriipd iKxlostrffifa 
Hall, Strophoiiicnd rlioyiihoiilidlis Wilckins. 'JMie u^jpermost 
25 or ;}() feet of the Pentamerus beds resume the texture 
of the basal portion, becoming generally much harder and 
more flinty, often showing on fresh fracture a steel gray color 
