June, 1906. New Forms of Concretions — Nichols. 29 



is a chain of four sand-calcite balls from Clermont. (Plate XX, Fig. 1.) 

 This consists of four spheres between 140 and 160 millimeters in 

 diameter united into a slightly curved chain 49 centimeters long. 

 The spheres where they join interpenetrate for perhaps one-eighth to 

 one-twentieth of their respective diameters. Each ball s nearly 

 spherical with no marked flattening and is simple. The only compli- 

 cation of form is an abrupt change in diameter of the spheres giving 

 each the external form of a laminated body from which the external 

 shell has been half broken away. This is, however, a consequence of 

 differing rate of growth for different sides of the sphere and is in no 

 wise dependent upon internal structure. These deposits, which are 

 associated with mineral springs, are doubtless more or less tufaceous 

 in character. 



The sand-calcite concretions of Saratoga Springs, New York, 

 tend to form sheets by the coalescence of many ind.viduals and thus 

 much of the material is better described as sandy calcareous tufa 

 than as concretionary. The two specimens shown in Plate XXI 

 illustrate this phase. These are respectively 15 x 40 and 17 x 20 

 centimeters in area and both are from 3 to 6 centimeters thick. Both 

 specimens are fragments evidently broken from consideraMy larger 

 sheets. The individual concretions from these sheets are forms 

 modified from the sphere by agencies which have p oduced a flatten- 

 ing and elongation, so that the simplest form of common occurrence 

 is a somewhat flattened ovoid or pear (Plate XXI, Fig. 1) with the 

 same appearance of lamination which occurs upon the Paris Basin 

 specimens. The larger number of those concretions which unite to 

 form a sheet of tufa at Saratoga Springs are much more elongated 

 than these pear shapes. Many of these more elongated forms so 

 coalesce as to lose their identity and present merely a solid, wavy 

 surface. When the individuality is not so completely lost, there 

 arise, first, shapes resembling a long-necked gourd, then, as the 

 elongation becomes greater, the flattening becomes greater also, the 

 form becomes wavy in both the horizontal and vertical planes and 

 deep, strong, longitudinal and occasionally transverse striations 

 appear. Thus the elongated individuals forming these sheet-like 

 bodies of concretion tend to become flat and more or less curved. 



Besides the tufaceous sheets, separate individual concretions 

 are common among the Saratoga Springs material. These show 

 little or no flattening and sometimes but little departure of any kind 

 from a spherical form. They are frequently heavily striated in a 

 meridional direction by deep grooves which come together at two 



