132 SYNOPSIS OF AMERICAN FOSSIL BRAGHIOPODA. [bull. 87. 



? Family EIOHWALDIID^ Schuchert, 1893.' 



Primitive or aberrant, rostrate Stropliomena(jea, witli narrow lateral 

 grooves and ridges for articiilatlou. Delthyriiim closed by a concave 

 plate ( fdeltidium). Pedicle emerging through the ventral umbone and 

 moving with growth anteriorly by resorption through the shell, as in 

 Siphouotretidffi. 



Eichwaldia Billings, 1858. | Dictyonella Hall, 1867. 



1. Family BILLINGSELLID^ Schuchert, 1893. " 



Strophomenacea with well-developed cardinal areas and deltidium. 

 Cardinal process obsolete or very rudimentary. Articulation fairly well 

 developed. 



Billingsella Hall and Clarke, 1892. 



Protorthis Hall and Clarke, 1892. 



2. Family STROPHOMENID.E King, 1846. 



Strophomenacea with well-developed cardinal areas, deltidium, chi- 

 lidium, cardinal and articulating processes. 



2a. Subfamily Rafinesquinin^ Schuchert, 1893. 



Leptsenacea Brauu, 1840; Orthiaida' (partim) d'Orbigny, 1847; Davidsonid* King, 

 1850; Davidsoniu;H Gill, 1871; Strophomeniua? (partim) Gill, 1871; Waagen, 1884; 

 Cadomellinie Munier-Chalmas, 1887; Leptyenidte Hall and Clarke, 1895. 



Strophomenoids with ventral valve convex and dorsal concave, except 

 in Strophonella. The relative form of the valves is the reverse of the 

 Orthothetinse. 



Ralinesquina Hall and Clarke, ' Pholidostrophia Hall and Clarke, 



1892. 

 Leptaena Dalman, 1828. 



Leptagonia McCoy, 1844. 



1892. 

 strophonella Hall, 1879. 



Amphistropbia Hall and Clarke, 1892. 



Strophomena Meek, 1873 (not Blain- Cadomella M.-Chalmas, 1887. 



viUe, 1825). Leptella Hall and Clarke, 1892. 



Plectambonites CEhlert, 1887 (not 

 Pander, 1830). 



Stropheodonta Hall, 1852. 



Brachyprion Shaler, 1865. 

 Donvillina (Ehlert, 1887 



Plectambonites Pander, 1830. 



Leptii-na Davidson, 1853; CEhlert, 

 1877 (not Dalman, 1828). 

 Lepta^nisca Beecher, 1890. 



Leptostrophia Hall and Clarke, ^^^"stiania Hall and Clarke, 1892. 

 ^gQ9 I Davidsonia Bouchard, 1847. 



'In 1893 the writer referred this family with doubt to the Rhynehoiiellacea. The absence of crural 

 plates in Eichwaldia forbids that disposition. If the concave plate closing the umbonal i)edicle 

 passage is a deltidium, there can be no doubt that this family belongs to the Protremata. Students 

 should searcli for the very young of Eichwaldia or Dic^tyonella, since it is through ontogeny alone 

 that the true systematic position of this family will be determined. 



