CHAPTER XXII. 



The Pearl Oyster's Representative — The Arks — The 

 Pea-Pod Shell— Modiola— The Mussels— Capt. Dix- 

 on's Account — River Clams — Pisidium — Sph.erium — 

 Kelly Shells— Lucina — Lazarina. 



r PHE family of the Aviculidce, Av-i-cu'-li-dse, which 

 1 in the Gulf of California furnishes the large and 

 beautful Pearl oyster, Meleagrina margaritifera, 

 Ivinn., Mel-e-a-gri'-na mar-gar-i-tif-e-ra, is poorly 

 represented on our coast. In the vicinity of Santa 

 Barbara there is a minute, white, oval shell, one- 

 eighth of an inch in length, named Bryophila setosa, 

 Cpr., Bry-of-i-la se-to'-sa, which belongs to that 

 family. 



Among the Arks, which are so numerous and fine 

 on the Atlantic coast, we also have but few. 



We name first, Barbatia gradata, Sby.,Bar-ba r -shi-a 

 gra-da'-ta. Height much greater than its length, 

 valves fully arched, somewhat angular, many ribbed. 

 Breadth one-fourth of an inch or more, color, light 

 brown; found under stones; southern. 



Milneria minima, Dall, Mil-ner'-i-a min'-i-ma, 

 resembles the last; but is smaller, curved, and marked 

 with fewer ribs. Recurved at the base; often minute. 



Axinea intermedia, Brod. , Ax-in'-e-a in-ter-me'-di-a. 

 Shell solid, white, tinged with brown, nearly circu- 

 lar. Inner edge finely crenulated. Pallial line 

 entire; hinge area crescent-shaped and marked by 



