13G 



SYNOPSIS OF AMERICAN FOSSIL BKACHIOPODA. 



[bull. 87. 



Si/nopsis of the divisio7i8 of Brackiopoda higher than genera. 



Superorders. 



Orders. 



Pedicle common 

 to both valves 

 throughout 

 life or Duly 

 in y outhf ul 

 growth. (Ho- 

 mocaulia.) 



Pedicle opening 

 common to 

 both valves 

 throughout 

 life. No del- 

 tidial i)lates. 

 Inarticulate. 

 (Atremata.) 



Pedicle opening 

 common to 

 both valves 

 only in youth- 

 ful growth. 

 D e 1 1 i d i a 1 

 plates usually 

 present. (Te- 

 lotremata.) 



Supe r/a rnilies. 



Shells rounded. 

 Pedicle short. 

 Animal not 

 burrowing. 

 (Obolacea.) 



Shells elongate. 

 Pedicle long. 

 Animal bur- 

 rowing. (Lin- 

 gulacea. ) 



Brachia sup- 

 ported by 

 crura. (Ros- 

 tracea.) 



Bracbia suj) 

 ported by 

 loops. (Tere- 

 bratulacea.) 



Brachia sup- 

 ported by spi- 

 ralia. (Spiri- 

 feracea.) 



FaTnilies. 



Valves semicircular; pedi- 

 cle opening more or less 

 large : 



Valves rounded, posteri- 

 orly acuminate; pedicle 

 opening small 



Valves round or oval, thick, 

 with solid or excavated 

 platforms ; 



Shells thin, elongate, with 

 oboloid interiors 



Shells thin, elongate, with 

 muscular system highly 

 specialized 



Shells elongate, with solid 

 platforms : 



Shells primitive. Ko del- 

 tidial plates ; articula- 

 tion rudimentary 



Articulation and deltidial 

 plates well developed 



Loops free, developing di- 

 rect ; no metamorphoses ; 



Loops free, developing in- 

 direct 



Loops attached to a me- 

 dian septum; developing 

 indirect ; 



Crura directly continuous 

 with bases of primary 

 lamellae between which 

 are the spiralia 



Crura directly continuous 

 with bases of primary 

 lamellae which are be- 

 tween the spiralia 



Bases of primary lamellfe 

 between the spiralia, and 

 sharply reciirving dor- 

 sally at their junction 

 with the crura 



Paterinidaj. 



= Obolidae. 



Trimerellidie. 

 Lingulellidae. 



LingulidaB. 

 Lingulasmatidae. 



Protorhyucliid;!'. 

 Ehynchonellidie. 

 Centronellidaj. 

 Terebratulidae. 



Terebratellidae. 

 = Atrypidae. 

 = Spiriferidse. 



=: AthyridsB. 



