244 
Kirtley F, Mather 
lete in many specimens; constrictions present on many indi- 
viduals with about 5i/^ to a, volution, rounded and faint; venter 
smooth except for constrictions. 
The sutures so far as known, only the external lobes and 
saddles being observable, are of the typical Gastrioceras type. 
Dimensions of Two Individuals. 
Diameter 5.2 mm. 5.0 mm. 
Height of last whorl 2.3 mm. 1.9 mm. 
Width of umbilicus 1.6 mm. 1.3 mm. 
Breadth 2.8 mm. 2.6 mm. 
Height of last whorl above surface of next preceding.. ..1.1 mm, 1.2 mm. 
Remarks. That these little shells represent mature indi- 
viduals is apparent from the fact that over a dozen of them, 
all approximately the same size, are at hand and none of them 
are associated with ammonoids of a large size. The presence 
of the constrictions and umbilical ribs is also indicative of 
maturity. 
Horizon and locality. Brentwood limestone: near Fayette- 
ville, Arkansas (Stations 134 and 135). Morrow formation: near 
Wagoner, Oklahoma (Station 294). 
TRILOBITA 
PROETlDHd 
Genus GRIFFITHIDES Portlock 
Griffithides morrowensis n. sp, 
Plate XVI, -figures 13-1 4-ci. 
Description. Cephalon semi-elliptical in shape, about two- 
thirds as long as wide, measuring the length from the anterior 
extremity to the posterior edge of the neck ring, moderately 
tumid ; the genal angles prolonged into spines of unknown 
length; cephalic shield with a striated border passing entirely 
around its periphery and terminating in the genal spines at 
either posterior angle; the border wide and sharply deflected 
to a nearly vertical position posteriorly, gradually becoming 
less oblique and more narrow anteriorly until in front of the 
glabella it approaches a horizontal position and is about two- 
thirds as wide as its posterior width, modified posteriorly by 
a broad, shallow, rounded depression, occupying more than half 
