1893,] NEW YORK ACADEMY OF SCIENCES. Ill 



the flocculeut, light-brown material, containing fragments of 

 other tests. The trilobites are preserved either in calcite or the 

 bi'own phosphate, with usually a dark line or band at the edges, 

 to which, doubtless, is due the black, shining surface which 

 they show when broken out of the rock. 



The foraminiferaare many chambered, with the cells grouped 

 apparently much like Globigerina ; but they are not perfect 

 enough to determine exactly. The smaller bodies referred to 

 MonadUes are numerous, and of three forms — round or oval, 

 pear-shaped, and urn-shaped. They sometimes have two 

 chambers, and rarely three. They show very often, long, 

 straight or curved, slender spines, and also what seem to be 

 stems on which they grew. (The spines very probnbly repre- 

 sent the whip of the flagellate infusoria, to which sponge- 

 gemmules have been referred.) 



Towards the surface of the nodvile, the brown phosphate 

 becomes more dense, and an opaque ring sharply separates it 

 from its matrix. Sometimes the central j^art is darker, and 

 separated from the outer zone by a similar dark ring ; or it 

 may be distinct on one side, and fade out into the lighter part 

 on the other. 



The matrix may be of the same phosphatic material, but is 

 more generally of glauconite grains, mixed with small angular 

 fragments of quartz. Its coarseness then contrasts strongly 

 with the fine grain of the phosphate. The glauconite is in 

 irregular masses, averaging aViu diameter, and often appearing 

 as if made up of a number of small coalescing grains. Smaller 

 round or oval grains are also common. 



The gray sandy layers are composed of small grains of quartz 

 and plates of mica, the latter almost always- lying in the plane 

 of bedding. In the fine shale there is an abundant groundmass, 

 probably argillaceous, and comparatively few of the larger 

 fragments. 



The nodules from Zone 3 are rather different from those of 

 Zone 2, and show considerable variety in structure. The mass 

 of the sandstone is made up of angular fragments of quartz, 

 and more rounded ones of calcite, with a tine dark-colored 

 cement, more or less ferruginous. Near the nodules, grains of 

 glauconite almost entirely replace the quartz, the calcite still 

 being abundant. Sometimes each grain is coated with a thin 

 dark layer of phosphate, and the cement is largely or entirely 

 the flocculent phosphate. 



The nodules themselves are much less pure than those of 

 Zone 2, and contain much foreign material, mostly minute plates 

 and shreds of mica. The large grains of quartx and calcite. 



