BRACHIOPODA. 355 



Family BILLINQSELLIDM Schuchbrt. 

 BiLLINGSELLA,* Hall, 1892. 



Family CLITAMBONITID.'E, N. H. Winchell and Schdchbbt. 



Protorthis, Hall, 1892. Hemipronites, Pander, 1830. 



PoLYKECHiA, Hall, 1892. Orthisina, d'Orbigny, 1847. 



Clitambonites, Pander, 1830. Scenidium, Hall, 1860. 



Pronites, Pander, 1830. Mystrophora, Kayser, 1871. 



Gonambonites, Pander, 1830. 



Family STRICKLANDINIID^. 



Syntrophia, Hall, 1892. Stricklandinia, Billings, 1859. 



Family CAMARELLID^. 



Camarella, Billings, 1859. Porambonites, Pander, 1830. 



Parastrophia, Hall, 1893. Isorhynchus, King, 1850. 



Anastrophia, Hall, 1879. Noetlingia, Hall, 1892. 



Brachymerus, Shaler, 1865. Lycophoria, Lahusen, 1885. 



(?) Branconia, Gagel, 1890. Camarophoria, King, 1846. 



Camarophorella, Hall, 1893. 



Family PENTAMERID^. 



CoNCHiDiUM, Linn^, 1753. Sieberella, (Ehlert, 1887. 



Gypidia, Dalman, 1828. Capellinia, Hall, 1893. 



Antirhynchonella, Quenstedt, 1871. Pentamerella, Hall, 1867. 



Zdimir, Barrande, 1879. Gypidula, Hall, 1867. 



Pentamerus, Sowerby, 1813. Amphigenia, Hall, 1867. 

 Barrandella, Hall, 1893. 



* The genus Billiitosblla, in correspondence with its early geological age, presents an elementary 

 structural aspect indicating that it may have served as a point of departure for the Obibid^ and 



STMOraOMMllIDM. 



