88 BRACHIOPODS. 



straight, or a little arched backward; area high, transversely 

 and vertically striated, ranging more or less nearly at right 

 angles to the plane of the valves, and flattened or somewhat 

 arched backward, with its lateral margins moderately well-de- 

 fined ; foramen large, or about two-sevenths as wide at the 

 hinge-line as the length of the latter, and three-fifths as wide 

 as high, showing its deep-seated transverse septum and tube 

 to be well developed above within. 



Surface of both valves ornamented on each side of the 

 non-costate mesial fold and sinus by about eighteen to twenty 

 simple, depressed, rounded, radiating costse, some five or six 

 of which on each side of the lateral extremities of both 

 valves are usually nearly or quite obsolete. Crossing all of 

 these on well-preserved specimens, numerous fine concentric 

 striae and some stronger marks of growth may be seen, and 

 over the whole a minute pitting may be observed, so crowded 

 and arranged as to present a delicate appearance, as seen by 

 the aid of a magnifier. (Meek.) 



Horizon and localities. Lower Carboniferous, Kinder- 

 hook beds : Clarksville ( Pike county ) ; Louisiana, Hannibal ; 

 Burlington limestone : Springfield. 



Syringothyris plena (HALL). 



Plate xl, fig. 8. 



Spirifer plenus Hall, 1858 : Geology Iowa, vol. I, p. 603, pi. xiii, figs. 4a e. 

 Syringothyris? plena Schucbert, 1890: Ninth Ann. Rep. State Geologist 

 New York, p. 37. 



A large heavy shell, distinguished from the associated 

 forms by its large curved area. 



Horizon and localities. Lower Carboniferous, Burling- 

 ton limestone : Hannibal. 



Syringothyris texta (HALL). 



tipirifer texlus Hail, 1857: 10th Rep. Reg. State Cab. Nat. Hist., p. 169. 

 Spirifer subcuspidatus Hall, 1858: Geology Iowa, vol. I, p. 646, pi. xx, 



fig. 5. 



Spirifer propinguus Hall, 1858 : Geology Iowa, vol. I, p. 647. 

 Spirifer subcuspidalus Hall, 1867: Pal. New York, vol. IV, p. 249. 

 Spirifer propinguus Meek & Worthen, 1868 : Geol. Sur. Illinois, vol. Ill, 



p. 530, pi. xix, fig. 8. 



