Memoirs Carnegie Museum, Vol. V. 



Plate XXXIII. 



1. Bivibranchia protradila Eigenmann. (Type.) 115 mm. No. 1873. 2a-2e. Gills of left side, begin- 

 ning with the first at 2a. 3. Roof of mouth and gill-chambers, showing valves. 4. Floor of mouth and 

 gill-chamber. •">. Sagittal section, showing valves of the roof of the mouth. 



