60 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY, 
Montpelier Beds. 
Homogeneous textured white chalky limestone with flints, Feet. 
resting unconformably upon the Cambridge beds . . . . +500 
Cambridge Beds. 
Yellow colored granular limestones (blue before oxidation) 
alternating with clays, with many fossils. . . . . . . . +100 
Blue, black, and purple clays grading into above. . . . . +100 
Richmond Beds. 
Blue and black clays without calcareous beds grading down 
into thin alternating beds of clay and sandstone . . . . . . +2 
Purple colored clays, without regular lamination . . . . +26 7 
Slightly calcareous beds in above . . . tS +25 
Purple and blue-black arenaceous clays, es down to 
Ded of Groat Nivery soe o oa u, +200 . 
The clays and marls are black and unctuous in some places; in others | 
they are yellow, excessively calcareous, aud full of minute Foraminifera 
(Miliolide), and grade from black into blue and gray colors upon drying, 
and into yellow on oxidation. The Foraminifera are so abundant that | 
they give an oólitic look to some of the rocks, but on oxidation they | 
crumble into small specks of pulverulent lime. This lime, after solu- 
tion and redeposition, largely makes the segregations of limestone. 
Sometimes the clay seams are so bituminous they have the appearance 
of thin lignitie beds. 
The limestones oceur in layers of various thickness up to two feet; 
they are nodular and irregular both in thickness and texture. At some 
places they are firmly indurated, at others they are friable and shaly. 
They are clearly chemical and clastic segregations in the great mass of | 
clays, and gradually increase in proportion as we ascend in the series, 
while the clays similarly decrease. In freshly exposed portions the . 
limestones are also blue-black in color. On weathering they become | 
bright yellow, as a result of the oxidation of small amounts of iron | 
which accompany the fossil colonies. | 
Many fossils — Echinoderms, Corals, Rudistes, and other Mollusca — | 
which are listed in another chapter of this report, occur in the cale | 
careous portions of these beds, both as free shells in the clays or | 
making the greater mass of the limestones, Some of the latter in the |. 
cuts south of Catadupa are almost entirely composed of Rudistes, which | 
also occur more sparingly in the beds at Cambridge. Oysters and | 
