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 Terehratula terminates, 
namely just behind the adductor muscle (fig. 2, v), seems to 
imply that it discharges through the byssal/oramew ; and as the 
same arrangement exists in Terebratulina, 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 in the Spiriferidce as it is known to do 
in the Rhynchonellida and Terebratulida *. , 
The following illustration (fig. 2*) is from a drawing by Mr. 
Albany Hancock. 
Fig. 2*. Waldheimia jlavescens. 
Fig. 2*. a. adductors; r. retractors ; x. accessory retractors (anal muscles) ; 
p.p. pedicle-muscles ; z. function uncertain ; o. mouth ; v. vent; 1. loop ; t. den- 
tal socket. 
* The muscular system of Ter. Jlavescens was correctly (though 
diagramatically) represented and described by Mr. King in his Memoir 
of the Permian Fossils, published by the Palaeontographical Society in 
1850 ; the function of the retractor muscles was not stated, but must 
have been understood. ( Woodward, MS.) 
