TKENTON PElilOD. 61) 



MOLLUSCA. 



MOLLUSCOIDEA. 



Class BRACHIOPODA. 



Ordee ARTHROPOMATA. 

 Family STROPHOMENID^. 



Genus STROPHOMENA Raflnesque, 1827. 



Strophomena filitexta Hall. 



Plate IV, fig. 8. 



Leptmna filitexta HaU, 1847, Paleontology of New York, i, 112. 

 Strophomena filitexta Hall, 1859, ]2tli Reg. Rep. N. Y. State Cab., 70. 

 Strophomena filitexta Meek, 1873, Paleontology of Ohio, i, 83. 



Shell a little above medium size compared with other species of the 

 genus ; concavo-convex, semi-oval or subsemicircular in outline ; widest at 

 the hinge-line, or, in rare cases, a trifle narrower there than it is a little 

 farther forward ; sides generally fonning an angle of about forty or forty- 

 five degrees Avith the hinge-line ; lateral and front margins continuously 

 rounded, with a nearly semicircular curve. 



Dorsal valve depressed or flattened in the umbonal region, but some- 

 what regularly arching from that part to the front and lateral margins ; 

 beak hardly distinguishable as such; area very naiTOw, projecting directly 

 backward. 



Ventral valve broadly concave, except near the beak, where it rises into 

 a slight convexity ; beak small, not prominent ; area moderately high, its 

 posterior or outer border sloping a little laterally but not forming an acute 

 angle at the hinge-extremity with its cardinal or inner margin ; foramen 

 triangular and closed by a prominent pseudo-deltidium ; hinge-teeth well 

 developed ; dental laminge continuous from the bases of the teeth with a 

 prominent ridge, which almost or entirely encircles the concave depression 

 occvipied by the muscular scars ; this depression sometimes having a narrow 

 ridge extending longitudinally through its middle ; cardinal margin of the 



