Fauna of the Morrow Group 
115 
Fenestella morrowensis n. sp. 
Plate IV, figures 11, 11a. 
Description. Zoarium an undulatory foliar expansion prob- 
ably not exceeding 3 cm. in length or height, composed of rigid 
branches united at regular intervals by non-poriferous dissepi- 
ments. Branches bifurcating at irregular distances, rounded on 
the reverse, and bearing a strongly carinate, nodiferous, median 
ridge on the obverse; 14 or 15 branches in 10 mm. Dissepi- 
ments rounded on both faces, slightly expanded terminally, about 
one-half as wide as the branches. Fenestrules elongate sub-oval, 
broader on the reverse and with outline crenulated by the strong 
peristomes of the zooecial apertures on the obverse face ; eleven 
in 10 mm. longitudinally. Zooecia in two alternating rows sep- 
arated by a strongly carinate ridge along whose elevated summit 
small elongate nodes occur at intervals of about 0.5 mm. Aper- 
tures, 18 or 19 in 5 mm., typically 3 to each fenestrule with a 
fourth opposite the dissepiment; circular in outline, approxi- 
mately one diameter apart in the rows ; peristomes strongly ele- 
vated and complete ; circular opercula present in well-preserved 
material. 
Horizon and locality. Hale formation: East Mountain, Fay- 
etteville, Arkansas (Station 137). Brentwood limestone: near 
Fayetteville, Arkansas (Station 135). Morrow formation: near 
Ft. Gibson, Oklahoma (Stations 296 and 301). 
Genus ARCHIMEDES Lesueur 
Archimedes juvenis n. sp. 
Plate IV, figures 12, 12a. 
Description. Axis strong, from 5.0 to 5.7 mm. in diameter; 
volutions regular, 3% to 4l^ in 2 cm. ; shaft and flange not 
sharply differentiated one from the other, the flange appearing 
simply as a spiral thickening of the shaft; the concavities be- 
tween the flanges, although moderately deep, without a distinctly 
flattened floor to form the sides of the shaft ; the slopes from the 
apex of the flange to the shaft sub-equal above and below so 
that in most specimens it is impossible to say with certainty 
which is the top and which the bottom of the spiral until the 
shaft has been sectioned ; as seen in longitudinal section the lines 
