564 C. H. GORDON 
majority of cases they thin out without a trace of parting beyond, 
but not infrequently they are terminated abruptly by a cross- 
fracture or suture. Branching of the horizontal sutures is common 
and often the two branches meet again, thus inclosing lens-shaped 
masses of stone. | 
On surfaces showing both horizontal and oblique sutures it is 
observed that the columns are all at right angles to a common 
plane which is approximately the plane of sedimentation. In their 
descriptions of stylolites, Marsh, Grabau, and others state that the 
columns project at right angles from the opposing faces, but this 
is true, according to our observations, only of those sutures that 
follow the planes of sedimentation. Where the suture is oblique 
to this plane the columns are inclined, the inclination being greatest 
in those sutures which are most oblique to the plane of sedimenta- 
tion. Where the suture is at right angles to the plane of sedimen- 
tation, distinct columns are wanting, the suture appearing as a wavy 
or zigzag line apparently representing the variety of stylolitic 
structure termed “‘pressure-suture”’ by some authors. 
THEORIES OF ORIGIN 
Only brief mention will be made here of the earlier suggestions 
offered in explanation of this structure. Those desiring a fuller 
treatment are referred to Wagner’s exhaustive paper,’ which 
includes a fairly complete bibliography of the subject. 
Organism theory.—Eaton,? who appears to have been the first to 
offer an explanation of these structures, considered them to be of 
organic origin and named them “‘lignilites”’ in the belief that they 
were the columns of corals. Four years later, Kloden’ described 
them as a distinct species of organism under the name Stylolites 
sulcatus. These, however, had few followers, though Kloden’s 
name “‘stylolites”’ has been retained for the structure. 
Crystallization theory.—Bonnycastle in 1831 considered the 
structure as a mineral formed by infiltration. The mineral expla- 
Georg Wagner, Geologische und paleontologische Abhandlungen (Koken), N.F. 
(1913), Band XI (XV), Heft 2, pp. ro1-27, Plates X, XI, XII. 
2 Amos Eaton, Geology of New York, 1824. 
3 F. Kloden, Die Versteineringen der Mark Brandenburg (1828), 1834. 
