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SPINY COCKLE 



Cardium quadragenarium Conrad 



Plate 5, figure 1 



Description — The lar^e size and spiny i-ibs of this species of 

 Cardium will serve to identify it. 



Use — Though of large size it is too seldom taken to be of economic 

 importance and is included here merely for the sake of completeness. 



Distribution — Fonnd off shore from Santa Barbara southward. 



COCKLE 



Cardium corbis Martyn 

 Plate 5, figure 2 



Description — This is the chief of the species of Cardium reaching 

 an important size, and is the bivalve having the best claim to the term 

 cockle. The valves are marked with numerous bold radiating ribs, sep- 

 ai-ated by grooves which are prolonged at the margin to form inter- 

 locking i)oints as in the scalloj). Viewed from the end, the deeply 

 arched sliells give the animal a heart-shaped outline, and they are 

 souK'times known as "heart shells." 



Habitat and habits — In the North, this form is found on tide 

 fiats in bays or sounds, ^vhere it burrows barely beneath the surface, 

 or may be seen lying on top of the sand. In California living speci- 

 mens were found both in bays and on exposed beaches of coarse loose 

 sand:. It is a very active bivalve and corresponding to its habit of 

 shallow burrowing, has a strong, elongated foot and no siphon tubes, 

 tlie siphon holes being formed by fusion of the mantle margins at two 

 points. 



Use — An excellent food mollusk, commanding a good price in the 

 market, it is not handled commercially in California because of its 

 scarcity. For the same reason, there is little local use made of it. 



Distribution — Though widely distributed in California it does not 

 appear to reach the importance that it does on the tide flats of Puget 

 Sound and the Gulf of Georgia. It was present in Humboldt Bay, 

 Crescent City, Tomales Baj^ and on Humboldt Spits and in general 

 where the rock cockle (Papliia) is found, though alwaj's in smaller 

 uuml)ers. In Elkhorn Slough emptying into IMonterey Bay it is fairly 

 a])undant and of good size. Some were found in ]\Iorro Bay and 

 l)etween Oso Flaco Lake and Point Sal at the southern dlid of Oceano 

 Beach, where they were taken with the Pismo clam. In the latter 

 place the sand is coarser and softer than on Pismo Beach and 

 apparently better fitted for rapid burrowing. Shells were obtained at 

 various points south to San Diego and occasional reports of former 

 beds were ol)tained ])ut these seem to be of little importance. 



