CARPET-SHELL 53 



pallial sinus is very deep, and the posterior end 

 of the shell is slightly gaping. 



In all the markets of San Francisco may be 

 found excellent specimens of the next species, 

 Tapes staminea, Conr., Carpet-shell, shown in 

 Fig. 3, PL XIV. It is known among the market 

 men as the u Hard-shelled Clam." Tomales Bay 

 furnishes a good part of the supply, but it abounds 

 all along the coast. Tie valves are rounded, 

 full, strong, and marked by numerous narrow ra- 

 diating ribs, which are cut by successive lines 

 of growth. It has three strongly locked cardi- 

 nal hinge-teeth and an external ligament ; the 

 pallaial sinus reaches to the middle of the shell. 

 The outside of some varieties is very prettily 

 marked by reddish brown chevrons ; others are 

 nearly pure white. These mollusks burrow in 

 stony places, and can be dug out when the tide 

 is low. Length, one to three inches. 



Fig. 5, PI. XIY, represents one of the most 

 graceful of our bivalve shells, named Amiantis 

 eallosa, Conr., It is pure white, full in the center 

 but quite thin at the edges. Its sculpturing con- 

 sists of many rcunded, concentric lines, equal in 

 size to the intervening grooves. There are no 

 radial markings whatever. The lunule is small, 

 set beneath the prominent umbones. Ligament, 

 external ; pallial sinus, moderate ; hinge, with 

 complicated cardinal and- strong, short, lateral 

 teeth. This species is found to the south, and 

 sometimes is several inches long ; common length, 

 two inches. 



Petricola carditoides, Conr., is a Rock-shell, 



