The l^EW Species of Brachiopoda, 353 



Chonostrophia Helderbergia. 

 Plate 7, fig. 11. 

 Chonostrophia Helderbergia, Hall. Palaeontology of N. Y., vol. VIII, pt. 1, 

 p. 853, pi. XV b, fig. U. 1892. 



Shell tenuous, semielliptical in outline. Hinge-line straight 

 and making the greatest diameter of the valves. Yalves nearly 

 flat, the pedicle- valve being gently concave and the brachial cor- 

 respondingly convex. Cardinal areas very narrow; marginal 

 spines not observed. Teeth of the pedicle-valve well developed 

 on either side of the moderately broad delthyrium ; at their bases 

 arises a median septum, strongest at the point of beginning and 

 continuing for one-half the length of the valve. In the brachial 

 valve the crural plates are ver}^ short, subparallel to the hinge- 

 line and apparently coalesced with the short cardinal process. 

 No traces of muscular scars retained. 



Surface covered with a great number of exceedingly fine, sub- 

 equal radiating strice, all of which are apparent on the interior 

 of the shell, even to the bases of the teeth and crural plates. 



Lower Helderberg group (Shaly limestone). Albany county 



Strophalosia Rockfordensis. 



Plate 7, figs. 6-10. 



Strophalosia Rockfordensis, Hall. Palaeontology of N. Y., vol, VIII, pt. 1, 

 p. 353, pi. xvii a, figs. 1-3. 1892. 



Shell semielliptical in outline, somewhat elongate. Hinge- 

 line scarcely as long as the greatest diameter of the valves. Car- 

 dinal area well developed on each valve, that of a pedicle-valve 

 bearing a convex deltidium ; scar of attachment on the pedicle- 

 valve covering only the apical region. . Surface regularly convex, 

 depressed toward the cardinal angles ; bearing scattered spines, 

 of which there is a well-defined row of six or seven on the car- 

 dinal margin. There are faint, irregularly concentric wrinkles 

 among the spine-bases. Apex of the brachial valve convex, but 

 the valve rapidly becomes concave, being of somewhat less curva- 

 ture than the opposite valve. Surface with conspicuous, irreg- 

 ular, concentric corrugations, and a few short spines over the 

 pallial region. 



45 



