— 22 — 



because of their feeble burrowing' ability, of maintaining themselves 

 in the shifting sand or mud. 



The much larger gaper {Schizotliaerus nuUalli) occupies the beach 

 near these borers though the animals are usually found in the blue 

 mud farther from the entrance rather than in the clay, as they are not 

 true borers but require a firm and not too hard bottom into which they 

 slowly l)urrow with increasing size, apparently seldom or never moving 

 about. The great depth reached by the adult is easily spanned by the 

 long fused siphons, the largest of any of the species here treated 

 (except the geoduck), but discourages most diggers as flo^\dng sand 

 makes depths of two or three feet almost prohibitive. 



Along the inner side of the sand spit separating the lagoon from tlie 

 sea the bank is steeper and more abrupt than elsewhere and is formed 

 of coarse sand mixed with some fine gravel and shells. This extends 

 for rather more than half a mile ; beyond this point there is a gradual 

 change to black sand and then to black sandy mud. The coarse sand 

 is inhabited almost exclusively by SanguinolanoA nuttalli, sometimes 

 called the "purple clam," a thin-shelled form found at a depth of 

 12 or 13 inches lying not head downward, as do most clams, but on 

 the right side. It reaches the surface by two long separate yellowish 

 siphons, which are seldom seen, though the characteristic pair of holes 

 may easily be located. 



As the sand becomes muddy, another form appears which is also 

 present on all other muddy shores, and therefore the most widely 

 distributed species found in the lagoon and slouglis. This is Macoma 

 nasuta, the "bent-nosed" or "mud" clam. The term "mud" clam is 

 not distinctive, being a.pplied to other forms, but "bent-nosed" is truly 

 descriptive, as the clam, like Sancjuinolaria, lies on the side, but in this 

 case on tlie left side and the siphonate end is turned distinctly up, 

 that is, toward the right, to accommodate the upward directed siphons, 

 here also separate and long. Similai* locations, namely flats of fine 

 sand or mud in sheltered bays, are sure to yield the bent-nosed clam 

 anywhere along the California coast. 



The mud and muddy sand also shelters three species of "cockles," 

 Paphia stamiuca, known as the rock cockle, and two species of Chione 

 or hard-shelled cockles. The Chiones are just below the surface and 

 in consequence the shells may often be seen in walking over the exposed 

 flats. Paphia, on the other hand, though found on similar bottom, 

 burrows deeper, usually six or more inches for those of moderate size. 

 If the living clams are examined, it will be found that there is a 

 corresponding difference in the length of the siphons and the same can 

 be seen in the shells, the pallial sinus of Paphia reaching half way to 

 the scar of "the anterior adductor, while in Chione it is a mere notch 

 (figures 9 and 11). 



The firmer flats of relatively undisturbed fine, dark, muddy sand 

 are also the home of an interesting small species of razor clam, Tagelus, 

 the jackknife clam. This, like its relative of the open beaches, is an 

 active burrower, but unlike it, lives in a smooth-lined permanent burrow 

 which fits its enlongated cylindrical shell snugly. By means of its long 

 muscular foot it moves up or down the burrow rapidly and at the 

 bottom is well protected from enemies or the heat of the sun. When 

 at the top of the burrow it is still about its own length from the 



