— 47 — 



WEDGE SHELL 



Donax calif 'trnica Conrad 

 Plate 16, figure 1 



Description — This speeies is of less importance than the followin<; 

 one and is described only to prevent confnsion. It is a small form, 

 but little exceeding half an inr-h, smooth and firm, with interloekinor 

 fine crenulations at the margin. It differs from Donax laf/vigata, 

 which follows, chiefly in the nearly central position of the nmbos. 



Distribution — Tt ranges from San Pedro southward; specimens were 

 ohlaincd ;it Long Beach, Anaheim Slough, Newport Bay and False Bay. 



It seems fo freciuent more sheltered places than D. laevigata, being 

 found near the entrance to bays and in similar locations not directly 

 exposed to surf. 



COMMON WEDGE SHELL 



Donax laevifiata Deshajes 



Plate 16, figure 2 



Other name — Bean clam. 



Description — This is the smallest of the economic species, the 

 largest siK'cimen encountered measuring only an inch. The valves 

 are heavy and strong, deeply arched and marked by indistinct radiat- 

 ing lines and concentric growth lines of varying degrees of distinctness. 

 The form is strikingly different from any other species treated in the 

 present paper in that the posterior or siphonate end is abruptly 

 truncated or cut off, forming nearly a right angle at the umbos which 

 thus come to lie near the siphonate end of the shell instead of centrally 

 as in I), calif ornica. The margins of the valves are heavily crenulated 

 and these roughnesses interlock in the closed shell. The color varies 

 from white to blue and purple being often conspicuously striped. 



Habitat and habits — This species is, like the Pismo clam, found 

 on exposed sandy beaches though it appears at times to prefer some 

 slight degree of protection such as that afforded by a position near the 

 entrance to a bay or behind a sand bar. Here they are found from 

 mid-tide down to low water at the surface or only slightly buried. The 

 siphons are separate and short, but little exceeding the width of the 

 shell, and in consequence they can not feed at any great depth. Often 

 on the exposed sand it will be found with the blunt siphonate end pro- 

 jecting nearly half the length of the shell above the surface. In 

 many of the specimens the siphonate end is provided with a wisp of 

 what appears to the clam diggers as "whiskers." These are in reality 

 a group of small plant-like colonial animals called hydroids which have 

 here found attachment as they might upon a rock and are not part 

 of the clam. From a tabulation of the position of a large number of 

 these clams is was found that the majority were placed "broadside" to 

 the sea with the hinge directed either up or down the coast. Whether 

 this plays some part in food getting or is of mechanical advantage in 

 keeping the position in the surf could not be determined. Where 

 present they are usually very abundant so that they may be sifted 



