BRACHIOPODA — TELOTREMATA. 345 



CXI. Hustedia Hall and Clarke. 

 Differs externally from RliyncJiospira only in its much coarser 

 plications. Internally it differs in the structure of the hinge plate 

 and in the presence of a split and weak tube attached by one side 

 to the deltidial plates. Carbonic. 



392. H. mormoni (Marcou). (Fig. 442.) Carbonic. 



Both valves more or less gibbous. Umbo prominent 

 and arched. Surface marked by 14 to 17 simple radiating ribs. 



Widely distributed throughout central and western United 

 States. 



CXII. Trematospira Hall. 



Spiriferoid, transverse with nearly equally convex valves. Hinge 

 line straight with abruptly rounded cardinal extremities. Surface 

 plicate. Pedicle valve with median sinus; beak truncated by a 

 circular foramen ; delthyrium covered by two short plates resting 

 upon the umbo of the opposite valve. 

 Teeth prominent. Brachial valve with 

 a median fold and with small and deep 

 dental sockets. Cardinal process very 

 prominent and elevated, divided into 

 four parts by a deep longitudinal and 

 a less prominent transverse groove. 

 Distinguished externally from Rhyn- 



. , rIG. 443. Irematospii'd camitra 



chouclla and Spirifcr by its punctate /p a j N Y n ) 

 structure. Siluric-Devonic. 



393. T. camura Hall. (Fig. 443.) Siluric. 

 Small, transversely elliptical to subrhomboidal. Valves almost 



equally convex. Sinus of pedicle valve marked by one or two 

 small plications which die out. toward the beak. Fold of brachial 

 valve with two small plications which likewise become obsolete 

 toward the beak. Surface marked by four to six plications on each 

 side tne median line and by concentric growth lines. 

 Niagaran of New York. 



394. T. multistriata Hall. Devonic. 

 Brachial valve the more convex. Surface granulose or punctate, 



marked by many fine radial striae and by concentric growth 

 lamellae. 



Helderbergian of New York. 



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