ON OOLITES AND SPHERULITES 599 
in the Onondaga Sea, just to the northwest of this locality, is 
correct." . 
These observations render it probable that other sedimentary 
siderite deposits, especially such as are closely associated with 
Fic. 1.—Photomicrograph of oGlitic grains of a light green silicate in a groundmass 
of siderite and (secondary) iron hydroxide, forming a local facies of the Onondaga 
limestone near Preston, Bath County, Kentucky. Note the free edges of the siderite 
crystals extending into the odlitic grains, cutting through their structure, mostly 
without disturbing it; also the discordance between outline and structure of the grain 
near the lower margin. (The longest diameter of this grain measures 0.7 mm.) 
caustobioliths (black shales, coal, etc.), first separated out in the 
colloidal form and subsequently assumed crystalline character. 
7C. R. Stauffer, “The Middle Devonian of Ohio,”’ Geol. Surv. of Ohio, ath Ser., 
Bulletin 10, r909, Pl. 14; C. Schuchert, A Text-Book of Geology, Part II (New York, 
to15), Pl. 15B; C. Butts, “Geology and Mineral Resources of Jefferson County, 
Kentucky,” Kentucky Geol. Surv., Ser. 4, Vol. III, Part II, Fig. 3. 
