SCHUCHERT.] 



KEY TO BRACHIOPOD FAMILIES. 



Superorders. 



Synopsis of the divisions of Bracliiopoda higher than genera — Coutinned 



ir/Jflrs Orders. fiii/ne.r families. Families. 



137 



Pediclo reBtrict- 

 ed to ventral 

 Yiilve through- 

 out life or onlj' 

 iu youthful 

 growth. (Idi- 

 oraulia.) 



Pedicle restrict- 

 ed to ren- 

 tral valvo 

 throughout 

 life. Inartic- 

 ulate. (Neo- 

 tremata.) 



Superfamilies. 



Pedicle aper- 

 ture modified 

 hy a deltidi-  

 um. (Acro- 

 tretacea.) 



Pedicle slit 

 modified hy 

 a list rium. 

 (Discinacea. ) 



Pedicle sup- 

 pressed. (Cra- 

 uiacea.) 



Pedicle restrict- 

 ed to ven- 

 tral valve 

 throughout 

 or a portion 

 of life. Artic- 

 ulate. (Pro- 

 tremata. ) 



' Shells without 

 spondyliaand 

 cruralia.<J 

 (Strophomen- 

 acea.) 



Shells with 

 spondyliaand 

 cruralia.{ 

 (Peutamera 

 cea.) 



Families. 



Pedicle opening small, cir- 

 cular, posterior to pro- 

 teg iilum 



Pedicle fissure narrow, 

 elongate, anterior to pro- 

 tegulum 



Pedicle fissure marginal, 

 open posteriorly 



Pedicle fissure narrow, 

 elongate, closed posteri- 

 orly 



Shells partially or com 

 pletely cemented to for 

 eigu hodies 



Pedicle opening large ; del- 

 tidium and articulation 

 incipient. No crural 

 process = 



Rostrate, aberrant Stro- 

 phomenacea 



Cardinal areas and deltid- 

 iuui well developed. No 

 cardinal process 



Cardinal areas, deltidium, 

 chilidium, and cardinal 

 process well developed : 



StrophomenidiB with im- 

 pressed brachial furrows 



Valves more or loss cov- 

 ered with hollow, anchor- 

 ing spines 



Cone-shaped productoids 

 completely modified by 

 cementation 



Delthyrium usually large, 

 open; deltidium devel- 

 oped only in early 

 growth 



Large, straight cardinal 

 areas with prominent 

 deltidium. No cruralia : 



Straight cardinal areas, 

 prominent deltidium, 

 and short cruralia 



Shells intermediate in 

 structure between Syn- 

 trophiidie and Penta- 

 meridiB 



Shells rostrate, commonly 

 without deltidium. Cru- 

 ralia well developed 



Acrotretidie. 



Siphonotretidae . 

 r= Trematidse. 



= Discinidse. 



^ Craniidae. 



Kutorginidae. 

 EichwaldiidsB. , 



= Billingsellidis. 



Strophomenidse. 

 Thecidiidse. 



= Productidse. 



Richthofenidae. 



Orthidae. 



Clitambonitidae. 



Syntrophiidse. 



Porambonitidae. 

 = Pentameridae. 



