14 



BRACHIOPODA. 



Others, each with a double termination, are inserted in the hinge- 

 plate {p) of the dorsal valve ; the septum supports the visceral 

 membranes. 



The position at which the intestine of Terebratula terminates, 

 namely just behind the adductor muscle (fig. 2, v), seems to 

 imply that it discharges through the byssal/orflmera ; and as the 

 same arrangement exists in Terebraiulina, Kraussia, Argiope, and 

 in the recent Rhynchonella nigricans, it becomes probable that 

 such is the general rule ; in those extinct genera which have the 

 foramen closed at an early age, there is always an opening be- 

 tween the deltidium and the umbo of the smaller valve (e. g. in 

 Uncites gryphus), which has been mistaken for a byssal notch. 

 The foramen in the hinge-plate of Athyris shows that the intes- 

 tine took the same course vo. the Spiriferidce as it is known to do 

 in the Rhynchonellidce and Terebratulida *. 



The following illustration (fig. 2*) is from a drawing by Mr. 

 Albany Hancock. 



Fig. 2*. Waldheimia flavescens. 



Fig. 2*. a. adductors ; r. retractors ; x. accessory retractors (anal muscles) ; 

 p.p. pedicle-muscles ; z. function uncertain ; o. mouth ; v. vent ; /. loop ; t. den- 

 tal socket. 



* The muscular system of Ter. flavescens was correctly (though 

 diagramatically) represented and described by Mr. King in his Memoir 

 of the Permian Fossils, pubUshed by the Palaeontographical Society in 

 1850; t\x& function of the retractor muscles was not stated, but must 

 have been understood. {Woodward, MS.) 



