CHAPTEE Y. 



CT^ASSIFICATIOK OF THE BKACHIOPODA. 



HISTORICAL. 



Fabiiis Columna, in 1616, and Martin Lister, in 1678. were the first 

 to describe bracliiopods, calling them Conehce anomia'. Cxruudler, in 

 1774, was, however, the first to give a good ilhistration of a brachiopod 

 in TerebratulinacapHt-serpentis. In 1818 Lamarck recognized 5 genera, 

 including the operculate coral Calceola. Other genera were added by 

 Sowerby, Dalman, and Defrance, from 1820 to 1830, and in the early 

 forties abont 1,500 species had been defined. In 1819 King recognized 

 40 genera in 16 families, and Bronu, in 1862, knew nearly 2,000 siiecies 

 and 51 genera. At i)resent there are probably no fewer than 6,000 

 species known in 321 genera, grouped in 31 families, 9 snperfamiles, 4 

 orders, and 2 snperorders. 



Since 1858 the class Brachiopoda has been divided by nearly all sys- 

 tematists into two orders, based on the presence or absence of articu- 

 lating processes. These two divisions were recognized by Deshayes as 

 early as 1835, but not until twenty-three years later were the names 

 Lyopomata and Arthropomata given to them by Owen. These terms 

 have been generally adopted by authors, though some i^refer Inarticu- 

 lata and Articulata of Huxley, or Bronn's Ecardines and Testicardines. 

 Bronn, in 1862, and King, in 1873, while retaining these divisions, con- 

 sidered the presence or absence of an anal opening more important 

 than articulation, and accordingly proposed the terms Pleuropygia and 

 Apygia, and Trententerata and Clistenterata, respectively. In many 

 Paleozoic genera of Clistenterata it has been shown that an anal open- 

 ing was also present, and therefore the absence or presence of this 

 organ is not of superordinal value, Beecher writes:' 



The dorsal beaks of Amphigenia, Athyris, Cleiothyris, Atrypa, and Rliyncbonella 

 are usually uotched or perforate. The perforation comes from the uuion of the crural 

 plates above the lloor of the beak leaving a passage through to the apex. A similar 

 opening occurs between the cardinal processes in Strophomena, Stropheodonta, and 

 alliedgenera, and the chilidiura may also be furrowed, as in Leptwua rhomhoidaUs. This 

 character is evidently in no way connected with the pedicle opening, but points to 

 the existence, in the early articulate genera, of an anal opening dorsal to the axial 

 line, as in the recent Crania. This dorsal foramen was described and figured by King 



'Am. Jour. Sci., 3d series, Vol. XLIV, 1892, p. 147. See also King, A Monograph of the Permian 

 Fossils of Ent;lan<l, 1850; and ffihlert, Fischer's Manuel de Conchyliologie, Appendice, 1887. 



Bull. 87 8 113 



