98 
THK GEOLOGIST. 
Lign. 1. — Cast of Dorsal Vaive of Cyrlina sepfosa. 
a Adductor, or posterior occlusor. 
a' Adductor, or anterior occlusor. 
Fig. 
Lign. 2. — Magnified Views of Casts of Athyris ambigua. 
Internal cast of the dorsa/ valve. 1 Fig. 2. Internal cast of tien^rui valve. 
a Adductor, or posterior occlusor.* 
u' Adductor, or anterior occlusor. 
a Adductor, or occlusor. 
r Cardinal, or divaricator. 
* In order to avoid further repetitions, I may mention once more that the 
muscles the function of which is to open or separate the valves have recently been 
termed divaricators and accessory divaricators by Mr. Hancock ; and those the 
function of which is to act in the closing of the valves have been termed anterior 
and posterior occlusors by the .same distinguished zoologist. The divaricators are 
those usually termed " cardinal muscles " (" adductor brevis " of Owen ; " muscles 
