136 



SYNOPSIS OF AMERICAN FOSSIL BKACHIOPODA. 



[bull. 87. 



Synojisia of the divisions of Brucliiopoda higher than genera. 

 Superordem. Orders. 



Pedicle common 

 to both valves 

 throughout 

 life or only 

 in y outhf ul 

 growth. (Ho- 

 mocanlia.) 



I'eilicleoiiening 

 common to 

 both valves 

 throughout 

 life. No del- 

 tidial plates. 

 Inarticulate. 

 (Atremata.) 



Pedicle opening 

 common to 

 both valves 

 only in youth- 

 ful growth. 

 D o 1 1 1 d i a 1 

 plates usually 

 present. (Te- 

 lotremata.) 



Siijier/ainilies. 



Shells rounded. 

 Pedicle short. 

 Animal not< 

 burrowin 

 (Obolacea.) 



Shells elongate. 

 Pedicle long. 

 Animal bur- { 

 rowing. (Lin- 

 gulacea. ) 



Brachia sup- 

 ported by 



crura. ( Kos- 

 tracea.) 



Brachia sup 

 ported b J' 

 loops. (Tere- 

 bratulacea.) 



Families. 

 Valves semicircular; pedi- 

 cle opening more or less 



;= Pateriuida?. 



postori- 

 l)edicle 



Brachia sup- 

 ported by spi 

 ralia. (Spiri- 

 feracea.) 



large 



Valves roundeil, 

 orly acuminate 

 opening small ^^ Obolidai. 



Valves round oroval, thick, 

 with solid or excavated 

 platforms -^ 'i'rimerellid^e. 



Shells thin, elongate, with 

 oboloid interiors ^^ Liugulellidie. 



Shell.s thin, elongate, with 

 muscular system highlj' 

 specialized = Lingulida?. 



Shells elongate, with solid 

 platforms = Liugulasmatidse. 



Shells primitive. Ko del- 

 tidial plates ; articula- 

 tion rudimentary =^ Protorhyuchida'. 



Articulation and deltidial 

 plates well developed = Ehyuchonellid;e. 



Loops free, developing di- 

 rect; no metamorphoses = Centronellidie. 



Loops free, developing in- 

 direct = Terebratulidse. 



Loops attached to a me- 

 dian septum; develoi>ing 

 indirect ^ Terebratellidw. 



Crura directly continuous 

 with bases of primary 

 lamelhe between which 

 are the spiralia == Atrypidw. 



Crura directly continuous 

 with bases of primarj' 

 lamellffi which are be- 

 tween the spiralia = Spiriferidse. 



Bases of primary lamellfe 

 between the spiralia, and 

 sharply recurving dor- 

 sally at their junction 

 with the crura = Athyridae. 



