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 Camarophvrinf, 

 but without sinus, fold, and plica- 

 tions. Lower Carboniferous ; North 

 America. 



Order 4. TELOTREMATA. 

 Beecher. 



Flo . 



> .. 7 . T> -L T -jt ji Cdimirophorifi Schlothfiml, v. Hue):. I'l-niiian ; Gera, 



Articulate JBmchlOpoda, With the RCUSS. /, Shell, Vi- It, Cast. C, Interior of shell, en- 

 nnonjnn ahnrcil hu JtnfJi vnlrp* in 1{ir eil 0"% Cardinal process ; o, Cnim ; ./, Spoiidylium ; 



opening snared t>y oom waves in (J< Dentalplates of dorsa i valvtj; ,,,.-, Meiliai . 

 nepionic 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 calcareous crura, loops, or spiralia. 

 Prodeltidium ubsent. 



Superfamily 1. RHYNCHONELLACEA. Schuchert. 

 Rostrate, primitive Telotremata, ivith or without crura. Cambrian to Recent. 



Family 1. Protorhynchidae. Schuchert. 



Primitive Ehynchonellacea without' deltidial plates or crura. Cambrian and 

 Ordovician. 



Protorhyncha, Hall and Clarke. Biconvex PJiynchonellae with the fold 

 and sinus ill-defined. No cardinal process or dorsal median septum. Surface 

 with low radial plications. Ordovician. 



There are smooth-shelled, very primitive PJiynchonellae in the American 

 Lower Cambrian belonging to this family. 



Family 2. Rhynchonellidae. Gray. 



Ehynchonellacea with crura of greater or lesser length. Ordovician to Recent. 



Orthorhynchula, Hall and Clarke. Pihynchonellae 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. 



Rhynchotrema, Hall (Stenochisma, Conrad, 1839; and Hall, 1867). Thick- 

 shelled, often gibbous Pihynchonellae 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. 



Rhynchotreta, 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 



