292 CAMBRIAN BRACHIOPODA. 



under the terminology of Schuchert [1897, pp. 73-77]. I agree with Hall and Clarke [1892c. 

 p. 21] that the terminology of the English authors has claims for its adoption. F. Bloch- 

 mann [1900, p. 108] has proposed a set of terms for the muscles of the inarticulate brachiopods 

 that has much to commend it. The terminology of Albany Hancock [1859, p. 800] has been 

 extensively used by authors. The numbers in this correspond to the numbers given the termi- 

 nology of King, Schuchert, and Blochmann. 



Terminology of Hancock [1859, p. S00\. 



Inarticulates: Articulates: 



1. Anterior occlusors. 1. Anterior occlusors. 



2. Posterior occlusors. 2. Posterior occlusors. 



3. Divaiicator. 3. Accessory divaricators. 



4. Central adiustors. 4.1 ,. ^ , ,. , 



^ _ , ,. , . ^ Ventral adiustors. 



5. Jixternal adjustors. 5.) 



6. Posterior adjusters. 6. Dorsal adjustors. 



7. Peduncular. 7. Peduncular. 



Terminology of King [1873, pp. 5-6]. 



1. Anterior lateral. 4. Transmedians. 



2. Centrals. 5. Outside laterals. 



3. Umbonal. 6. Middle laterals. 



Terminology of Schuchert [1897, pp. 73-75]. 



1. Retractors. 5. Protractors (externals). 



2. Adductors. 6. Protractors (middles). 



3. Pedicle. 7. Diductors. 



4. Rotators. 



Terminology of Blochmann [1900, p. 108]. 



1. Lateralis. , 4. Obliquus internus. 



2. Occlusor anterior. 5. Obliquus extemus. 



3. Occlusor posterior. 6. Obliquus medius. 



DEFINITIONS. 



Adductor muscles {see Central muscles). — The term adductor is used in the description of 

 the muscles of the Protremata. 



Anterior lateral {retractor) muscles. — In the Atremata these extend from the outer lateral 

 margins of the visceral area in the ventral valve to its anterior extremity in the dorsal valve, 

 and serve to readjust the dorsal shell. 



Anterior region. — That portion of the shell in front of the transverse axis and opposite 

 the pedicle opening. 



Afex. — The place of initial shell growth. It may be the most posterior portion of the 

 valve or it may be situated near the transverse axis. 



Apical callosity. — The tliickened boss at the inner side of the apex of the ventral valve 

 of Acrotreta and other neotrematous genera, through which the pedicle tube or foramen passes. 



Area. — See Cardinal area. 



Articulate hrachiojyods. — In the orders Protremata and Telotremata the valves articulate 

 by means of teeth and sockets. In some Atremata rudimentary articulation is also developed. 

 (See p. 307.) 



Atremata. — Primitive inarticulate calcareophosphatic brachiopods with the pedicle emerg- 

 ing more or less freely between the two valves. For a more detailed description see "Classifi- 

 cation of Cambrian Brachiopoda," page 321. 



Bracliia. — The fleshy, coiled or spiral, ciliated appendages of brachiopods serving in 

 water circulation and respiration. 



Bracliioccele. — All of the anterior half of the valves outside of the anterior portion of the 

 parietal band. (After King.) 



Cardinal area. — A more or less well developed triangular area on each side of the delthy- 

 rium, distinctly set off from the general surface of the shell. It is best developed on the ventral 



