Fauna of the Morrow Group 
113 
in 5 rnm. ; zooecial walls comparatively thick, ridge-like at the 
surface and finely granulose. Zooecial tubes short, prostrate 
below, becoming erect above, perforated diaphragms not numer- 
ous. Zooecial cavities sharply defined one from the other, meso- 
pores and acanthopores absent. 
Remarks. Although no representatives of this genus have 
hitherto been described from the Pennsjdvanian strata of Amer- 
ica, there is no doubt that the material at hand should be thus 
identified. It is evidently not referable to any of the Mississip- 
pian species. 
Horizon and locality. Brentwood limestone: near Fayette- 
ville, Arkansas (Station 134). 
FENESTELLID^ 
Genus FENESTELLA Lonsdale 
Fenestella serratula Ulrich 
1890. Fenestella sem^atula. Ulrich, Geol. Surv. 111., vol. 8, p. 544, pi. 50, 
figs. 5-5c. 
Keokuk group: Nauvoo, Illinois 
Warsaw beds: Monroe County and Warsaw, Illinois. 
St. Louis limestone: Caldwell, Lyon, and Crittenden Counties, 
Kentucky. 
Chester group: Sloan’s Valley, Kentucky. 
1894. Fenestella serratula. Keyes, Mo. Ceol. Surv., vol. 5, p. 23. 
Keokuk limestone: Keokuk, Iowa. 
1911. Fenestella serratula. Morse, Proc. Ohio State Acad. Sci., vol. 5, 
p. 364, text fig. 5. 
Maxville limestone: Kroft Bridge, White Cottage and Harper 
Shaft, Olive Furnace, Ohio. 
This widespread and comparatively long-lived species of 
Fenestella is represented by numerous specimens from the Mor- 
row group though strangely it has not been recognized in collec- 
tions from the lowest horizon of the group. The material at 
hand is somewhat variable but typically there are 26 or 27 
branches and 18 or 19 fenestrules in the space of a centimeter 
with 26 or 27 zooecial apertures in 5 mm. The median keel 
which separates the two rows of alternating apertures is slightly 
flexuous and when well preserved displays the serrate crest 
typical of the species. The dissepiments are possibly somewhat 
stronger and less depressed than those of the Mississippian indi- 
viduals. 
