MUSEUM OF COMPARATIVE ZOOLOGY. 23 



two on each side of the septum.* The drumhead membrane, covering the 

 space inside of the brachia, was translucent white or opalescent, and quite 

 thick and tough toward the middle of each lobe. 



I am inclined to think that an error has been perpetuated in regard to 

 the position of the mouth of Megathyris decollata. It has been figured 

 and described by Woodward as being of a circular form, and situated in 

 the midst of the drumhead membrane. It is certainly not so situated in 

 Cistella ; and I do not believe that it is in Megatliyris, though I have only 

 seen dry specimens. In the present species it is placed, as in all the Tere- 

 bratulkhe, at the back of this membrane, just in front of the posterior 

 junction of the brachia, and at the bottom of a deep transverse groove 

 which is of a stout membranous consistency, and the two sides of which, for 

 convenience' sake, I have called the lips {labia). In the present species 

 the oral groove is situated far back and close to the brachia, which are ex- 

 ceptionally long behind it, as already described. It is, in fact, entirely 

 hidden by them until they are laid back. The groove is very long and 

 quite deep, the entrance to the oesophagus being trumpet-shaped and flat- 

 tened transversely. Were the brachia disjwsed as in Woodward's figure, 

 the oral groove would be hidden. I am disposed to think that this was 

 really the case in the specimen figured, and that the extraordinary circular 

 mouth there figured was an accidental lesion of the dry tissues, which might 

 easily be taken for a mouth in so small an animal. The labia, in all the 

 Brachiopods I have examined so far, have invariably exhibited a tinge of 

 darker color than the surrounding tissues. The present case forms no ex- 

 ception. The posterior lip presents a small prominence in the median 

 line, and the anterior lip a small emargination or concavity below this 

 prominence. This structure is also common to all the Brachiojwds I have 

 examined. 



The oesophagus is wide, transversely flattened, with thin walls, and of 

 an orange color. It enters the stomach nearly at a right angle, without 

 much dilation. The stomach is oval with thicker and firmer walls ; the 

 inner lining appearing slightly villous and rugose. The intestine is not 

 differentiated from the stomach on the lower side, but on the upper side a 

 deep groove occurs at the juncture. The canal is stout and thick at its 

 lower extremity, tapers slightly, and terminates in a somewhat bulbous, 

 but pointed cascal extremity, attached to the perivisceral membrane. The 

 various membranous bands which support the alimentary system present 

 no differences from the homologous structures in other species of the Tere- 

 bratuliike. The stomach was filled in each case with a yellowish flocculent 

 matter. The hepatic lobules resembled those of other species, entering 



* There is but one on each side, close to the hinge margin, in the last species. 



