II4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
graphic Board to Buffalo River [Wilmarth, 1938, pp. 181, 182] ).—The Buffalo 
River series consists, in ascending order, of the Everton, St. Peter, Dutchtown, 
and Joachim formations. These formations have not yielded brachiopods in the 
lower Mississippi area except Lingulella sp. 7 from the Dutchtown formation 
and are therefore not discussed in this paper. Their correlation is based on posi- 
tion in the section and fossils other than brachiopods. (Dake, 1921, pp. 14-28; 
Weller and St. Clair, 1928, pp. 91-104; for Dutchtown formation, see Cullison, 
1938, pp. 219-228.) 
Rock Levee formation.—This formation was proposed by Grohskopf (1948, 
p. 360) for part of the limestones referred by Ulrich (1939, p. 109) to the 
Murfreesboro formation in the vicinity of Cape Girardeau in Missouri. This 
formation takes some thickness from the underlying Joachim and the over- 
lying Plattin formations. Knowledge of this formation is derived from surface 
exposures and a study of deep wells. The name is from a siding on the St. Louis— 
San Francisco RR. in NW4NW4NW43 sec. 24, T. 30 N., R. 13 E., Cape 
Giradeau County. In the type area the thickness in wells is 270 feet but only 
about 50 feet appear on the outcrop at the junction of U. S. Highway 61 and 
Missouri Highway 74. The formation contains an upper zone 70 feet thick char- 
acterized by cystid plates; the remainder of the formation contains silt and sand 
in the residues. The formation is composed mostly of buff and gray dolomitic 
rock but the upper part is fine gray limestone. Fossils are not abundant, but 
the upper layers contain Ancistrorhyncha nussouriensis Cooper. Correlation is 
with the Peery limestone formation in the Appalachians because of similarity of 
the Ancistrorhyncha occurring in the two formations. 
PLATTIN GRouP.—The rocks to which this name is applied formerly had only 
formational rank. Larson (1951, pp. 2041-2075) recently raised them to the 
status of a group. Larson recognized four formations in ascending order: 
Bloomsdale, Beckett, Hager, and Macy. The Plattin group is prominent in east- 
ern Missouri from Scott County in the south to Ralls County at the north, and 
westward to eastern Callaway County. The group thins to the north, and all 
the member formations thin in the same direction. The maximum thickness is 
about 300 feet; near Mineola in its western range only 31 feet of the lower beds 
is exposed. 
Bloomsdale formation.—This is composed mainly of calcilutite and fine- 
grained dolomite with interbeds of oolite and limestone pebble conglomerate. At 
its thickest, near Beckett Mills, Ste. Genevieve County, it is mostly 59 feet of 
calcilutite but thins to about 12 feet at Kings Lake in Lincoln County. The forma- 
tion is sparsely fossiliferous as usual in calcilutites and, as usual in that lithology, 
Ancistrorhyncha (=A. costata Ulrich and Cooper) is common. hynchotrema 
(probably Rostricellula) sp. is also reported. Correlation is suggested with the — 
Wardell formation. 
Beckett formation.—This is a fine-textured limestone with intraformational 
calcarenite and carbonate pebble conglomerate. Chert is abundant in the upper 
part. The lower Beckett is pinkish-brown, fucoidal, and fine-textured. This part 
is absent north of Herculaneum, Jefferson County. The Upper Beckett contains 
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