118 SYNOPSIS OF AMERICAN FOSSIL BRACHIOPODA. |Hru..87. 



tlie Tiimerellid.e and Liugiilasmatidu' liave family strncturcs in com- 

 mon and were referred to the same family. Ontogeny and clironogene- 

 sis, however, show that the former famil^^ originated directly in the 

 Obolidu', while the latter was not evolved from the linguloid ])hyluiu 

 until the Obolidie had given origin to the Lingnlellidfe and the Linga- 

 lida'. Again, the family Terebratellidu', probably 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 gronp 

 (Magellanina^) passes through a series of loop metamorphoses difl'ercnt 

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

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

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

 writer, in 189'^, 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 Telotremata could not have 

 originated in the Pentameriida^, since no Pentanieracea are known in 

 the Cambrian uutil long after that order had representation. The 

 divisions Lyopomata and Arthropomata, introduced by Deshayes and 

 Owen, have been abandoned for reasons given in ])revious pages. 



CLASSIFICATION AND SYNONYMY.' 



Class BRACHIOPODA Cuvier, 1802; Duun^'ril, 1 



Spirobranchiophora Uray, 1821; Palliobranchiiita Blainville, 1824; BrancLiopotla 

 Eisso, 1826 (uot Latieille); Brachioixxlidai Broderip, 1839; Brauchiouopoda Agassiz, 

 1847; BracbionocephalaBronn, 1862; SiiirobranchiaBronii, 1862; Brauchionobranchia 

 Paetel, 1875. 



Bivalved MoUuscoidea witli 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, ])hosphatic 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 supi)orted in 

 the two terminal sui)erfamilies by an internal calcareous skeleton, or 

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

 Central nervous system consisting of an oesoi)hageal ring, with weakly 



' All uainuH in small tyjie anil indented arc synonyniw of ilie term in larf;( r typ<' ininicdiutily pre- 

 ceding. 



