OYSTERS AND SMALL CLAMS 



65 



l^urtonia occidentalism Dall, the Western Mullet- 

 shell, also lives in Bering Strait and northward. It 

 is said to be larger, stouter, and shorter than the last 

 species. 



We now come to the great sub-order Lucinacea, 

 named from the word Lucina, one of the titles of 

 the goddess Juno, in heathen mythology. The shells 

 internally are marked with one very long and nar- 

 row muscle-scar, while the other is nearly round. 

 The pallial line which joins them has no sinus. Fig- 

 ure 39 gives two 

 views of ^hya- 

 sira hisecta^ Con- 

 rad, the Cleft 

 Thyasira, which 

 was found in 

 the deep water 

 of Puget Sound 

 by Prof. O. B. 

 Johnson. It has 

 also been found 

 in the far north. It is the largest species of the 

 genus, sometimes measuring two or even three inches 

 across. The figure plainly shows its peculiarities. 



'thyasira barharensis^ Dall, the Barbara Thyasira, 

 resembles the last, but the beaks are more nearly in 

 the center. It was formerly known as Cryptodon or 

 Axinus. It ranges along the coast from Washington 

 to Mexico. The shell is white and chalky externally, 

 and measures 17 mm. in length. 



T^hyasira excavata^ Dall, the Sculptured Thyasira, 

 has a thin, white shell, with a yellowish epidermis. 



Fig. 39. X I (*) 



