NO. 2 BRACHIOPOD SUPERFAMILY STENOSCISMATACEA GRANT 31 



boniinae. The Psilocamarinae are characterized by modifications of 

 the hinge plate and intercamarophorial plate. In Psilocamara and sili- 

 cate Camarophorina the hinge plate is undivided, but the intercamaro- 

 phorial plate is entirely absent. The trend toward costation became re- 

 established weakly in Permian Cyrolexis n. gen., whose hinge plate is 

 complete or perhaps shallowly recessed at the anterior, but whose 

 intercamarophorial plate is very short and thin, or absent. 



The hinge plate of Camarophorinella Licharev is deeply divided, the 

 intercamarophorial plate entirely absent, and the edges of the poste- 

 rior part of the camarophorium attach directly to the sides of the hinge 

 plate. Externally, the genus bears little resemblance to others of the 

 Psilocamarinae, its shape and costation most nearly resembling Seden- 

 ticellula of the Atriboniinae. 



The edges of the posterior part of the camarophorium meet the 

 hinge plate also in the sulcate and typically smooth genus Camaro- 

 phorina. If Lower Carboniferous shells from England prove to belong 

 to this genus, it will be the earliest known member of the Psilo- 

 camarinae. 



FAMILY STENOSCISMATIDAE 



This family probably originated from Atribonium during the Devon- 

 ian. The earliest genus with a stolidium is Coledium n. gen., although 

 Devonian and Early Mississippian species of that genus lack that struc- 

 ture. Late Paleozoic members of the family can be divided into two 

 subfamilies on the basis of retention or atrophy of the stolidium, and 

 rhynchonelliform or uncinuliform shape. 



Subfamily Stenoscismatinae. — The stolidium and a normal rhyn- 

 chonelliform shape characterize the two genera of this subfamily. 

 Coledium extends from the Late Devonian into the Permian, and 

 Stenoscisma Conrad began in the Late Mississippian and continued 

 through the Permian. The stolidium is best developed in this genus. 

 Species of Stenoscisma whose beaks are relatively straight have the 

 delthyrium constricted by deltidial plates that appear typically rhyn- 

 chonelloid. Many later species have the pedicle beak tightly curved over 

 the brachial beak, thus constricting or closing the delthyrium. Costa- 

 tion is highly variable among the Stenoscismatinae, but internal struc- 

 tures are entirely normal for the superfamily, with spondylium, cama- 

 rophorium, hinge plate, and intercamarophorial plate consistently and 

 proportionately developed in all species. 



Subfamily Torynechinae. — The two genera of this subfamily are 

 externally uncinuliform and strongly costate ; inner structures are 

 normal for the superfamily according to present knowledge. Septa- 

 camera Stepanov of the Late Pennsylvanian and Early Permian may 



