NO. 2 BRACHIOPOD SUPERFAMILY STENOSCISMATACEA GRANT 27 



The sulcate genus Camarophorina includes individuals with the ped- 

 icle beak tightly pressed against the brachial valve, and others with the 

 beak suberect and the foramen small but open. Perhaps both the at- 

 tached and the free modes of life were available to species of this genus, 

 although those with the foramen closed must have lived unattached. 



Camerisma ranges from the Mississippian into the Permian without 

 a known individual whose pedicle foramen is open in the slightest de- 

 gree. This smooth form, with its high vaulted fold, necessarily must 

 have lived free on the substrate, either in the sediment or in vegetation. 

 Ivanova (1949, p. 109) discussed the morphology and inferred living 

 habits of the exceptionally strongly trilobate species C. pentameroides 

 (Tschernyschev), which she assigned to Stenoscisma. Other species 

 exhibit the same adaptations to life on the bottom sediment, namely 

 the deepened and thickened umbonal region of the pedicle valve which 

 provided a posterior center of gravity, and sufficient height to keep the 

 anterior of the shell above the sediment while the posterior lay partly 

 buried. In addition, Ivanova pointed out the broad overlap of the pos- 

 terolateral edges of the valves which provided a seal that enabled the 

 valve to gape at the anterior and remain effectively closed at the poste- 

 rior. This overlap is found in all genera whose pedicle foramen is 

 closed. The highly arched fold also helped to place part of the gape 

 above the sea floor, beyond the reach of most sediment. 



The Permian genus Cyrolexis is characterized by tight apposition 

 of the beaks that provides no opening for a pedicle. The globular shell 

 probably could not remain stationary, balanced on its pedicle valve like 

 Camerisma. Therefore both valves are somewhat thickened and deep- 

 ened at the posterior, and the fold is not high. The shell could rest on 

 either valve with the posterior center of gravity keeping the anterior 

 gape above the substrate. The valves overlap strongly at the sides to 

 provide a seal against sediment as in other free living genera, although 

 the overlap extends proportionately farther to the anterior in Cyro- 

 lexis. 



ORIENTATION 



Attached shells probably rotated on their pedicles, changing their 

 orientation at different times (Rudwick, 1962). Shells that attached to 

 upper surfaces of the substrate probably kept the pedicle valve upper- 

 most for more of the time, and those attached to under surfaces prob- 

 ably hung more often with the brachial valve up. 



Free-living forms could have assumed any orientation. Those that 

 fell into tangles of Bryozoa or vegetation could have settled in any atti- 

 tude. Those that settled on the sediment of the sea floor probably were 

 rolled or flipped by currents or other animals. However, the stolidium 



