398 MOLLUSCOIDEA phtlüm v 



Rhynchotetra Weller. Elongate, coarsely plicate shells nearest to 

 Camarotoechia. Dental lamellae uniting iiito a spondylium, which is supported 

 by a median septum. Lower Carboniferous ; North America. 



Tetracamera Weller. Like Camarotoechia, but with rostral dorsal cavity 

 divided into four Chambers by the crural plates and a median septum. A 

 spondylium present, but practically without septal support. Lower 

 Carboniferous ; North America. 



Paraphorhynchus Weller. Coarsely plicate Rhynchonellae with fine 

 additional Striae. Interior much as in Camarotoechia. Lower Carboniferous ; 

 North America. 



Leiorhynchus Hall. Internally like Camarotoechia, but with the plications 

 on the lateral slopes usually faint or obsolete. Devonian to Carboniferous. 

 ^ubgenus : Moorefieldella Girty. Differs in having a finely plicate surface. 

 Lower Carboniferous ; North America. 



Wilsonia Kayser {Uncinulina Bayle). Sub-cuboidal or sub-pentahedral 

 Rhynchonellae with the low plications marked anteriorly by fine median lines. 

 Internally as in Camarotoechia. Silurian to Lower Carboniferous. North 

 America and Europe. 



Hemiplethorhynchus von Peetz. Very similar to Camarotoechia. Crural 

 cavity with a posterior triangulär opening. Upper Carboniferous ; Altai, 

 Kussia. 



Hypothyridina Buckman {Hypothyris King, non Hubner 1822). Sub- 

 cuboidal Rhynchonellae with a very rudimentary dorsal median septum. 

 Plications as in Wilsonia. Vascular sinus frequently strongly impressed in 

 the ventral valve. Devonian ; North America and Europe. 



Pugnax Hall and Clarke. Rhynchonellae with a deep dorsal and shallow 

 ventral valve, and very prominent fold and sinus. Dental lamellae short ; 

 no median septa. Devonian to Carboniferous ; North America and Europe. 

 Subgenus : Ällorhynchus Weller. Has decided angular plications as in 

 Camarotoechia. Lower Carboniferous ; North America. 



Fugnoides Weller. Exterior like Pugnax, with the internal characters of 

 Camarotoechia. Lower Carboniferous ; North A.merica. 



Shumardella Weller. Much like Pugnax, but with a short dorsal median 

 septum that is not connected with the hinge-plate. Lower Carboniferous ; 

 North America. 



Rhynchopora King (Rhynchoporina QEhlert). Plicate Rhynchonellae with 

 the shell substance punctate. A crural cavity as in Camarotoechia, but roofed 

 over by the hinge-plate. Dental lamellae well developed. Eange from 

 Lower Carboniferous to Permian ; Europe and North America. 



(?) Torynifer Hall and Clarke. May be Rhynchonellae with the crural plates 

 united into a hinge-plate. Genus not yet defined. Lower Carboniferous ; 

 North America. 



Terebratuloidea Waagen. Rhynchonellae with very large apical truncate 

 foramen, but without dental plates or median septa. Carboniferous to 

 Permian ; India. 



Rhynchonella Fischer (as restricted by Hall and Clarke) (Fig. 592, A). 

 Sub-pyramidal pauciplicate shells with the pedicle opening as in Cyclothyris. 

 Dental lamellae and a dorsal median septum present. Jurassic and 

 Cretaceous. 



Cyclothyris M'Coy (as redefined by Buckman in 1906) (Figs. 592, B, 



