118 SYNOPSIS OF AMERICAN FOSSIL BRACHIOPODA. [nrLL.87. 



tlie Tiiinevellidii' and Lingulasmatidie liave family structures in com- 

 111011 and were referred to the same family. Ontogeny and cbronogeiie- 

 sis, however, show that the former family originated directly in the 

 Obolidu", while the latter was not evolved from the linguloid i)hyluin 

 until the ObolidM' had given origin to the Lingulellida^ and the Lingu 

 lidii'. Again, the family Terebratellidie, i^robably during early Mesozoic 

 times, divided, one stock drifting into boreal and another into austral 

 regions. These two stocks agree in the earliest shelled condition and 

 at maturity, but between these two stages of growth the austral grou]) 

 (MagellaniiKc) passes through a series of loop metamorphoses difl'ereut 

 from that through which the boreal group (Dalliiue) passes. Therefore 

 it is unnatural to include botli in one subfamily, as was formerly done. 

 It was by the application of the above-mentioned principles that the 

 writer, in 1893, arranged all brachiopod genera under the four orders 

 instituted by Beecher. Since then this subject has received consider- 

 able attention, and the many Cambrian brachiopods brought together 

 by Walcott have been examined as to their generic structures. These 

 studies have led to some changes in the classification which follows, 

 the most important being that the order Telotreraata could not have 

 originated in the Pentameriida;, since no Pentameracea are known in 

 the Cambrian until long after that order had representation. The 

 divisions Lyoponiata and Arthropomata, introduced by Deshayes and 

 Owen, have been abandoned for reasons given in previous j?ages. 



CLASSIFICATION AND SYNONYMY.' 



Class BRACHIOPODA Cuvier, 1802; Dum^ril, 1 



Spirobrancliiophora Gray, 1821; Palliobranchiata Blaiuville, 1824; Branohiopoda 

 Kisso, 1826(uot Latreille); Bracliiopodida^ Broderip, 1839; Brancliionopoda Agassiz, 

 1847 ; Brachionocephala Bronn, 186- ; Spirobrauchia Bronu, 1862 ; Braiichionobranchia 

 Paetel, 1875. 



Bivalved Molluscoidea with inequivalved, equilateral shells attached 

 to extraneous objects by a posterior prolongation of the body, or pedi- 

 cle, (1) throughout, (2) during a portion of life, or (3) cemented ventrally. 

 Valves ventral and dorsal. In composition, phosphatic or calcareous, 

 or both. Animal consisting of two pallial membranes intimately re- 

 lated to the shell. Within the mantle cavity at the sides of the mouth 

 are inserted the two, more or less long, oral, usually spirally enrolled, 

 cirrated brachia, which are variously modified, and are supported in 

 the two terminal superfamilies by an internal calcareous skeleton, or 

 brachidium, attached to the dorsal valve. Anus present or absent. 

 Central nervous system consisting of an oesophageal ring, with weakly 



' AH iianu's in small type an<l indentetl are syuonyiiis of iho term in larger type immediately pre- 

 ceding. 



