130 SYNOPSIS OF AMERICAN FOSSIL 15RACHIOPODA. 1 hill. 87. 



1. Family AOROTRETIDyE Sclnicliert, 1803. 



Acrotretacea with the pedicle o])enins' i)()steriov to the piotegulum. 



Acrotliele Linnarsson, 1876. Conotreta Walcott, 1889. 



Limiarssoiiia Walcott, 1885. fMesotreta Kutorga, 1848, 



Disciuopsis (Matthew) Hall and fOrbicella d'Orbigny, I84i). 



Clarke. 1892. i Kfiyserlin,i,Ma Pandftr, 1861. 



Aerotreta Kutorga, 1848. | ?HeImerseiiia Pander, ISCl. 



2. Family SIPHONOTRETIDyK Kutorga, 1S48. 



Acrotretacea with the pedicle opening passing by resoiption aiiteri 

 orly through the protegnlum and the umbo of the shell. 



Yorkia Walcott, 1897. Protosiphon Matthew, 1897 



Trematobolus Matthew. 1893. Schiziiinbon Walcott, 1884. 



Siphonotreta de Verneuil, 1845. ! .Schizamboiiia (Kblert, iss?. 



8u])ei-taniily DISCINACEA Waagen, 1885. 

 ]>aik:iulia (]>ariiin) Waag«'u, 188"); Diac.aulia (partiin) Hall ami Clarke, 18!t5. 



Neotremata with phosphatic shells, alistriiuu. but witli no deltidinm. 

 Dorsal protegnlum usually subceutral. 



1. Family TREMATID^E Schuchert, 1893. 



Priuiitive Discinacea, in which the posterioi' niargiu of the ventral 

 valve has ;i triangular pedicle notch throughout life. A listrinm is usu- 

 ally present. 



Discinolepis Waagen, 1885. 

 Trematis Hharpe, 1847. 



Orbicella Hall and Whitfield, 1875 

 (not (l'Orl)igny, 1810). 

 Schizocirania Hall and Whitfield, 

 1875. 



Schizobolus Ulrich, 188(1. 

 Linguiodiscina Whitfield, 1890. 

 ffihlertella Hall an«l Clarke, 1890. 

 "? Mouobolina Salter, 1805. 



2. Family DTSCINIDJ5 Gray, 1840. 



()rl)i(^iiliila- McCoy, 1814. 



Derived Discinacea with an open pedicle notch in early life in the 

 posterior margin of the ventral valve, which is closed posteriorly dur- 

 ing neanic growth, leaving a more or l^ss long, narrow slit i)artially 

 closed by the listrium. 



Orbiculoidea d'Orbigny, 1847. I l^iscina Lamarck, 1819. 



Schi/Otreta Kutorga, 1848. Orhicula Sowerliy, 18.30 (not Cuvier, 



Lindstrd-mella Hall and Clarke, 1798). 



1890. Disciiiisca Dull, 1S71. 



Ha'merella Hall and Clarke, 1890. , 



