396 MOLLUSCOIDEA phylum v 



Camarophorella Hall and Clarke. Biconvex, sub-circular CamaropJioriae, 

 but without sinus, fold and plications. Lower Carboniferous ; North America. 



Strophomenacea of unknown relationships. 



Family 1. Eichwaldiidae Schuchert. 



Primitive or aberrant, rostrate Strophomenacea, with narrow lateral grooves and 

 ridges for articulation. Delthyrium closed hy a concave plate {? deltidiiim). Pedicle 

 emerging through the ventral umbone and moving with grotvth anteriorly hy resorption 

 through the shell, as in Siphonotretidae. Ordovician and Silurian. 



Eichwaldia Billings. The single species of this genus has a smooth 

 exterior. Ordovician ; North America. 



Dictyonella Hall {Eichwaldia auct.). Exterior surface of valves pitted in 

 quincunx, resembling Trematis. Silurian ; North America, England, Bohemia 

 and Gotland. 



Order 4. TELOTREMATA Beecher. 



Specialised (through Atremata, 1 Obolacea), articulate, calcareous Brachio- 

 poda, with the pedicle opening shared by both valves in earliest shelled 

 stages, usually confined to one valve in later stages, and becoming more or less 

 modified by deltidial plates in advanced growth stages. Brachia supported by 

 calcareous crura, loops or spiralia. 



Superfamily 1. RHYNCHONELLACEA Schuchert. 



Rostrate, primitive Telotremata, with or without crura for the support of the 

 hrachidia. Pedicle foramen nearly always beneath the leak and but rarely through 

 a truncate ventral apex. Shells almost always impunctate. Ordovician to Eecent. 



Family 1. Protorhynchidae Scluieheit. 



Primitive Ilhynchonellacea without deltidial plates or crura. Ordovician. 



Protorhyncha Hall and Clarke. Biconvex Phynchonellac with the fold 

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

 with low radial j)lications. Ordovician ; North America. 



Family 2. Rhynchonellidae Gray. 



Bhynchonellacea with crura of greater or lesser length. Shells usually plicate, 

 rarely smooth or spinose. Ordovician to Recent. 



Sul)family A. Rhynchotreminae, novum. 



RhynchoneUids with a cardinal process. Ordovician to Devonian. 



Orthorhynchula Hall and Clarke. Ehynchonellae with short, straight hinge- 

 line and cardinal areas in both valves, bisected mesially by open delthyria. 

 Teeth unsupported by dental lamellae. A linear cardinal process present. 

 Ordovician ; North America. 



Rhynchotrema Hall (Stenochisma Comad, 1839; and Hall, 1867) (Fig. 590). 



