ORDER IV TELOTREMATA 323 
more or less strongly plicated. Spondylium supported by a long median 
septum. Devonian to Permian ; 
Europe, India, and North America. 
Camarophorella, Hall and Clarke. 
Biconvex, sub-circular Camarophoriae, 
but without sinus, fold, and_ plica- 
tions. Lower Carboniferous; North 
America, 
Order 4. THLOTREMATA. ) 
Beecher. : Fic. 542. 
F abs a Camarophoria Schlotheimi, v. Buch. Permian; Gera, 
Articulute Brachiopoda, with the Reuss. 4, Shell, 1. B, Cast. C, Interior of shell, en: 
pedicle opening shared by both valves in gel Gyr Carthsl pode: Chun 2, Spondy tin 
nepnic and early neanic stages, usually 
confined to one valve in later stages, and becoming more or less modified by deltidial 
plates in ephebic stages. Brachia supported by caleareous crura, loops, or spiralia. 
Prodeltidium absent. 

Superfamily 1. RHYNCHONELLACEA. Schuchert. 
Rostrate, primitive Telotremata, with or without crura. Cambrian to Recent. 
Family 1. Protorhynchidae. Schuchert. 
Primitive Rhynchonellacea without deltidial plates or crura. Cambrian and 
Ordovician. 
Protorhyncha, Hall and Clarke. Biconvex Lhynchonellae with the fold 
and sinus ill-defined. No cardinal process or dorsal median septum. Surface 
with low radial pheations. Ordovician. 
There are smooth-shelled, very primitive Lthynchonellae in the American 
Lower Cambrian belonging to this family. 
Family 2. Rhynchonellidae. Gray. 
Lthynchonellacea with crura of greater or lesser length. Ordovician to Recent. 
Orthorhynchula, Hall and Clarke. Rhynchonellae with short straight hinge- 
line and cardinal areas in both valves, bisected mesially by open delthyria. 
External surface plicate. Teeth unsupported by dental lamellae. A linear 
cardinal process present. Ordovician ; North America. 
ELhynchotrema, Hall (Stenochisma, Conrad, 1839; and Hall, 1867). Thick- 
shelled, often gibbous Rhynchonellae with prominent, thick, concave deltidial 
plates. Dorsal valve with a thick median septum, upon which rests a linear 
cardinal process. Crural| plates very broad and stout. Ordovician to 
Devonian ; North America. 
Lthynchotreta, Hall. Trihedral Rhynchonellae with the ventral beak acu- 
minate and produced. Pedicle foramen apical, the delthyrium being com- 
pletely closed by the deltidial plates. Dental lamellae and cardinal process 
present. The prominent dorsal median septum separates posteriorly, each 
