324 MOLLUSCOIDEA BRACHIOPODA SUB-KINGDOM v 



branch supporting one process of the divided hinge-plate. Silurian ; North 

 America and Europe. 



Camarotoechia, Hall and Clarke (Plethorhyncha, H. and C.) MhynchoneUae 

 .with the dorsal median septum bearing posteriorly an elongate cavity. 

 Cardinal process absent ; dental lamellae present. Ordovician to Carboni- 

 ferous ; North America andt Europe. 



Leiorhynchus, Hall. Like Camarotoechia, but with the plications on the 

 lateral slopes usually faint or obsolete. Devonian to Carboniferous. 



JPUsonia, Kayser (Uncinulina, Bayle). Sub-cuboidal or sub-pentahedral 

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

 Dental lamellae present. No cardinal process. Silurian and Devonian ; 

 North America and Europe. 



Uncinulus, Bayle. Like IFilsonia, but with the hinge-plate undivided, and 

 with a well-developed cardinal process. Devonian; North America and Europe. 



Hypothyris, King. Sub-cuboidal Rhynchonellae with a very rudimentary 

 dorsal median septum. Plications as in Wilsonia. Vascular sinus frequently 

 strongly impressed in the ventral valve. Devonian ; Jforth America and 

 Europe. 



Pugnax, Hall and Clarke. PJiynchonellae with a deep dorsal and shallow 

 ventral valve, and very prominent fold and sinus ; otherwise resembling 

 Hypothyris. Devonian to Carboniferous ; North America and Europe. 



Eato-nia, Hall. Pihynchonellae with large, flabellate, deeply excavated 

 muscular scars in the ventral valve. No dental lamellae. Cardinal process 

 large, resting upon a short median septum, and bifurcate at its summit. 

 Devonian ; North America. 



Terebratuloidea, Waagen. PJiynchonellae with very large apical foramen, 

 but without dental plates, cardinal process, or median septa. Carboniferous 

 to Permian ; India. 



Rhynchopora, King (PJiynchoporina, Oehlert). Plicate Pihynchonellae with 

 the shell substance punctate. Carboniferous to Permian ; Europe and North 

 America. 



Rhynchmetta, Fischer (as restricted by Hall and Clarke), (Fig. 543, A). 

 Sub-pyramidal shells with a prominent anterior linguiform extension. Dental 

 lamellae and a dorsal median septum present. No cardinal process. Jurassic 

 and Cretaceous. 



Upwards of 600 species of Rhynchonella have been described, most of which 

 are found in Mesozoic strata (Figs. 543, B, 544). It is probable that but few of these 

 agree with the "type species, R. loxia, from the Upper Jura of Russia. Hall and Clarke 

 have shown that many American Palaeozoic species belong to other genera ; and Bittner 

 has also removed from Rhynchonella many Triassic species. It is probable that no 

 Palaeozoic Rhynchonellae s.s. exist. 



Halorella, Bittner. Sharply plicated Rhynchonellae with a median sinus on 

 both valves. Alpine Trias. 



Austriella, Bittner. Small triangular, usually smooth-shelled Rhynchonellae 

 without prominent fold and sinus. Alpine Trias. 



Norella, Bittner. Like Austriella, but with prominent anterior fold and 

 sinus. Alpine Trias. 



Rhynchonellina, Gemellaro. Transverse Rhynchonellae with fine rad' 

 striae. Cardinal margin nearly straight, with a low concave ventral 



