446 Trans. Acad. Sci. of St. Louis. 



genus Spiriferina, but none of the specimens show the 

 punctate shell structure of that genus although the medium 

 septum and the strongly lamellose concentric surface mark- 

 ings are well developed. In the absence of the punctate shell, 

 this species agrees in all its generic characters with that 

 group of septate, lamellose, Spirifers which Schuchert has 

 included under the generic name Delthyris in a restricted 

 sense. 



The Glen Park specimens resemble Spiriferina clarJcsvill- 

 ensis of the Louisiana limestone, but are narrower, with a 

 smaller number of plications, and with more strongly convex 

 valves. They also resemble the Kinderhook species S. solidi- 

 rostris, but as well as being narrower with ifewer plications, 

 they lack the depression in the median line of the fold of the 

 brachial valve and the corresponding elevation in the sinus of 

 the pedicle valve of that species. Both of these species 

 agree with the Glen Park specimens in the lack of the punc- 

 tate shell, and the proper generic reference of all three 

 species is probably Delthyris rather than Spiriferina^ and 

 they might be compared with the Hamilton species D. sculp- 

 tilis, although all are very distinct from that species. 



Delthyris suborbicularis n. sp. 



Plate 1, figs. 27-28. 



Description. Shell small, subelliptical in outline, wider 

 than long, the hinge-line shorter than the greatest width of 

 the shell. Pedicle valve moderately convex, with a strong 

 medium septum internally, the beak obtuse and not incurved; 

 cardinal area rather small, slightly concave, sloping backward 

 and forming an angle of about 130° with the plane of the 

 valves; sinus rather shallow, concave in the bottom; lateral 

 slopes convex, each marked by five or six simple, rounded 

 plications, the cardinal margin rounding into the cardinal 

 area. Surface marked by strong concentric, lamellose lines 

 of growth. Brachial valve not seen. 



The dimensions of the type specimen, a pedicle valve, are : 

 length 10.5 mm., width 11.5 mm., convexity 3 mm. 



JRemarJcs. This species is far less abundant in the Glen 



