CLASSIFICATION CAMBRIAN BRACHIOPODA — WALCOTT I47 



iieanic growth, leaving a more or less long, narrow slit partially 

 closed by the listrium. 

 Orbiciiloidca 



Superfamily CRANIACEA Waagen, 1885 



Cemented calcareous specialized Neotremata without pedicle or 

 anal openings at maturity. 



Family CRANIID^ King, 1846 



Craniacea with the pedicle functional probably only during nepi- 

 onic growth. 



Philhedra 



Order PROTREMATA Beecher, 1891 (emend) 



Progressive (though atrematous Kutorginacea), articulate cal- 

 careous Brachiopoda with well-developed cardinal areas. The 

 pedicle opening is restricted to the ventral valve throughout life or 

 during early growth and is often modified and more or less closed 

 by a deltidium. Often there is a chilidum. Brachia unsupported 

 by a calcareous skeleton other than crura. 



Superfamily ORTHACEA Walcott and Schuchert, new 



Derived, progressive Protemata. Cruralia and rudimentary spon- 

 dylia (pseudospondylia) free or cemented (through sessility) directly 

 to the valves. Sometimes without deltidia and chilidia. Cardinal 

 process more or less well-developed except in the most primitive 

 genera. 



Family BILLINGSELLID^ Schuchert, 1893 



Primitive Orthacea with an open or more or less closed delthyrium. 

 Cardinal process well developed, rudimentary, or absent. Usually 

 with a clearly defined pseudospondylium, to which the muscles of 

 the ventral valve were attached. Shell structure dense, granular, 

 lamellar, non-fibrous. 



Subfamily NISUSIIN.li Walcott and Schuchert, new 



Primitive Orthacea with more or less well-developed deltidia and 

 with or without rudimentary chilidia. Spondylia and cruralia rudi- 

 mentary or small and not supported by septa. Cardinal process 

 rudimentary or absent. 

 Nisusia 



(JauicscUa) 

 Pro tort his 



(Lopcria) 



