934 Report oF THE STATE GEOLOGIST. 
Family Turcirips, Gray. 
Thecidea, Defrance, 1882. . | Bactrynium, Emmrich, 1885. 
Lacazella, Munier-Chalmas, 1880. Pterophloios, Giimbel, 1861. 
Thecidiopsis, Munier-Chalmas, 1887. Davidsonella, Munier-Chalmas, 1880. 
Thecidella, Munier-Chalmas, 1887. Lyttonia, Waagen, 1883. 
Eudesella, Munier-Chalmas, 1880. Oldhamina, Waagen, 1883. 
Family RicurHorentp2, Waagen. 
Richthofenia, Waagen, 1883. 
Family BittrineseLim.s», Schuchert. 
Billingsella,* Hall, 1892. 
Family Criwamesonttip2, N. H. Winchell and Schuchert. 
Protorthis, Hall, 1892. Hemipronites, Pander, 1830. 
Polytcechia, Hall, 1892. Orthisina, d’Orbigny, 1847. 
Clitambonites, Pander, 1830. Scenidium, Hall, 1860. 
Pronites, Pander, 1830. Mystrophora, Kayser, 1871. 
Gonambonites, Pander, 1830. 
Family SrrickLaNpInuD®. 
Syntrophia, Hall, 1892. ; | Stricklandinia, Billings, 1859. 
Family CamMargLup®. 
Camarella, Billings, 1859. Isorhynchus, King, 1850. 
Parastrophia, Hall, 1893. | Noetlingia, Hall, 1892. 
Anastrophia, Hall, 1879. _Lycophoria, Lahusen, 1885. 
Brachymerus, Shaler, 1865. 
(?) Branconia, Gagel, 1890. 
Porambonites, Pander, 1830. 
Camarophoria, King, 1846. 
Camarophorella, Hall, 1893. 
Family PenraMerip®. 
Sieberella, Ghlert, 1887. 
Capellinia, Hall, 1893. 
Pentamerella, Hall, 1867. 
Conchidium, Linné, 1753. 
Gypidia, Dalman, 1828. 
Antirhynchonella, Quenstedt, 1871. 
Zdimir, Barrande, 1879. Gypidula, Hall, 1867. 
Pentamerus, Sowerby, 1813. Amphigenia, Hall, 1867. 
Barrandella, Hall, 1898. 
*The genus Billingsella presents, in correspondence with its early geological age, an ele- 
mentary structural aspect indicating that it may have served asa point of departure for the 
Orthides and Strophomenide. 
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