205 



Brachiopoda. 



(I. HA^'ASAKA). 



Strophomenidae. 



Orthotetes, Fischer. 

 Orthotetes erenistria (Phill.) FuEcii. 

 PI. XXIV., Figs. 6 and 7. 



1911. Ort/io^/ieUs crfmstrier, FKi:cu :— -v. RlcUTHOFEi^'^ Ch'msi, vol. V., 

 p. 76. pi. 10, fig. 6. 



The specimens now under consideration were first studied by Prof. Frech 

 when Prof. Yabe showed him the specimens several years ago. Of the three 

 lots of the species from the different localities in China then known to him, 

 the present material was selected as the type or the representative. One of 

 the two specimens was figured by him, and his description was based on it. 



The species was first introduced as Spirifcra crcnisti-ia b>' Phillps in the 

 second part of his '" Geology of Yorkshire " (1S36), and subsequently, as far 

 as the writer is informed, such generic names as StreptorliyiicJms, Orthis, 

 Orthothetes {Orthotetes), Schuchertclla or Schellzvtcnclla were attached to it. 

 In 190S, GiRTY^^ planned a general classification of the Carboniferous Ortho- 

 tctinae, and many of the allied genera was arranged and correlated to each 

 other. According to his system, the shells of Orthotetes are not plicated and 

 have " moderately developed dental plates in the ventral valve, which con- 

 verge and unite, inclosing with the pseudodeltidium a triangular pyramidal 

 chamber." Moreover, the convergent dental plates unite at their junction to 

 a median septum to form " a triradiate structure." 



On examining the Chinese specimens that are represented by two inner 

 casts of the shell, one finds that the dental plates, or Frech's " Zahnstutzen '" 

 are not convergent, but on the contrary, they are divergent, and also rather 

 short. They lack a median septum which is continuous with dental plates in 

 Orthotetes. Thus the Chinese specie-s represents an independent type to which 



i) G. H. GiRTY: — The Guadalupian Fauna, p. 164. 1908. 



