192 POTTSVILLE FAUNA OF OHIO 



Genus Hustedia Hall and Clarke 



Hustedia mormoni (Marcou) 

 PI. IX, figs 28, 29 



1858 Terebiatula mormoni, Marcou, Geol. North America, p. 51, PI. 6, Fig. 11. 



Mountain L. S.: Salt Lake City, Utah. 

 1894 Hustedia mormoni. Hall and Clarke, Int. to Study of Brach., Pt. 2. PI. 37, 



Figs. 13-20. 



Coal Measures: Near Kansas City, Missouri. 



Remarks. Although this little species is abundant and widely dis- 

 tributed in rocks of Pennsylvanian age, it is particularly characteristic 

 of the upper part of the system, so that its appearance in the basal 

 member of the Pottsville formation in Ohio is of interest, especially 

 as it has not been found in any of the higher members of that forma- 

 tion. The form is common in the Harrison ore, and with the exception 

 of a few cases where the entire shell has been replaced by calcite, it 

 occurs only as internal and external molds. Occasionally the spiralia 

 and crura are preserved. 



Dimensions. A specimen of average size measures: length 7 mm., 

 width 4.5 mm., convexity 4 mm. 



Horizon and locality. Harrison ore: Jackson County, Locality 

 1, c. 



Genus Composita Brown 



Composita subtilita (Hall) 

 PL VIII, figs. 10-13 



1838 Terebratula argentea. Shepard, Am. Jour. Sci., 1st Ser., Vol. 34, p. 152, Fig. 8. 



Limestone: Western bluff cf Little Vermilion River, Illinois. 

 1852 Terebratula subtilita. Ball, Stansbury's Exped. Great Salt Lake of Utah, p. 409, 



PL 2, Figs. 1, 2. 



Carboniferous: Missouri River, near Weston. 



/ 



Remarks. Composita subtilita constitutes without doubt the most 

 widely distributed and one of the most abundant fossils of the Pottsville 

 formation of Ohio. It is common in the Harrison and Sharon ores at 

 the base, and is found in almost every other fossiliferous horizon to the 

 Black Flint member at the top, although it occurs in great profusion 

 in the Lower Mercer and McArthur members. Specimens from the 

 Harrison ore often have the spiralia and even the jugum preserved in 

 an unusual manner. 



Dimensions. The measurements of a large specimen from the 

 Harrison ore are: length 18 mm., width 16 mm., convexity of ventral 



