3. Vulsella. Lam. 3V1. 



Shell longitudinal, sub- 

 equivalved, irregular ; 

 beaks equal. Fig. 89. 



( 2G ) 



Hinge with a pro- Ligament inserted in 

 jecting callosity on each the hollow. (1) 

 valve, depressed above, 

 bearing the impression 

 of a conical obliquely 

 arched hollow. 



4. Placuna. Lam. M. 



Irregular, flattened, Hinge preserving two 

 sub-equivalved, of a thin longitudinal sharp ribs 

 foliated substance and al- in the form of an in- 

 most transparent. Fig. 87. verted Y on one valve, 



and two corresponding 

 impressions on the 

 other. 



Ligament attached to 

 the impressions. (2) 



5. Anomia. Lin. M. 



Inequivalved, irregular, 

 adhering by the oper- 

 culum ; one valve perfo- 

 rated, generally flattened, 

 with a hole or slope at its 

 beak; the other a little 

 larger, concave and en- 

 tire. Fig. 90. 



Operculum small, el- 

 liptic, bony, with the 

 interior muscle of the 

 animal attached. 



Ligament interior and 

 cardinal. (3) 



(1) They are frequently found in the sponges of the Indian Ocean and New- 

 Holland. Foss. at Grignon. 



(2) M. Leschenault found pearls in the P lacuna sella, which differ in shape and 

 appearance from those generally found, fig. 88. Indian Ocean, Red Sea. 



(3) The Anomice, like the Ostrcce, always remain in the same place, and are 

 found in all seas. 



