DESCRIPTION OP SPECIES 319 



Remarks: This variety differs from 8. salteri in the more elongate 

 form, the length being much greater in proportion to the width. From 

 8. triplesiana of the Brassfield limestone it differs in the relatively greater 

 length of the shell and in the absence of a mesial fold or sinus. 



Horizon: Stricklandinia zone 18 to 25 feet above the base of the 

 Kankakee limestone, at Hamburg, along Kankakee Eiver above Custer 

 Park, and at Elgin, Illinois. 



Stricklandinia pyriformis var. vasculosa n. var. 

 Plate 16, Figure 6 



Description: Shells having the appearance of young forms of 8. pyri- 

 formis, but the surface of the casts marked by somewhat irregular ridges 

 of unequal size, three to five of which extend longitudinally along the 

 median portion. From the margins of this median area less prominent 

 ridges curve downward and outward over the lateral portions of the shells, 

 some of which divide once or twice before reaching the margin. The 

 markings on the surface of the casts indicate the presence on the interior 

 of the shells of a few longitudinal furrows in the median portion, from 

 the borders of which low, rather broad, often bifurcating furrows extend 

 downward and outward to the margins. 



The shell is ovate in outline; the hinge line shorter than the greatest 

 width ; the valves subequally convex, without fold or sinus ; the spon- 

 dylium is moderately deep, and is supported by a short medium septum; 

 the impressions of the crural processes are rather deep, slender, and some- 

 what diverging. 



Horizon and locality: In the Stricklandinia zone 18 to 25 feet above 

 the base of the Kankakee limestone, along Kankakee River near Custer 

 Park, and at Elgin, Illinois. 



Stricklandinia circularis n. sp. 

 Plate 16, Figure 4 



Description : Shell subcircular in outline ; length and width about equal, 

 the greatest width near the middle ; valves about equally convex ; hinge 

 line slightly longer than half the greatest width; cardino-lateral portions 

 and the front and lateral margins rather regularly rounded. 



. Ventral valve gently convex, the greatest convexity near the middle ; 

 medial portion depressed longitudinally from beak to front, forming a 

 shallow sinus, which becomes quite broad in the anterior half of the valve. 

 The surface is gently convex transversely over the anterior and lateral 



