;S() Edible Mi'lhisca ol the ()ri';^(ni (oasl 



prospered in tlie Siii>Iaw l\i\'er since its intn ulnction ahont fori}' 

 years a,L;(), there are certain local conditions which ina_\' in time 

 work toward its de])letion. The North lM)rk. a trihutary of the 

 Sinslaw River of considfrahle size, pours its fresh waters, after 

 a i)eriod of heav\- rainfall, over the tide tlats occu])ied hy the 

 clams. During- times of tintisnall\- hii^h water the tide Hats are 

 sometimes tlooded continnonsly tor several weeks at a time i)er- 

 mittin^- much silt and sand to he deposited on the surface of the 

 clam l:)eds. During' the latter part of Decemher \y)iy and through- 

 otU Januar\'. I<ji8. excessive rainfall caused exceedingly high 

 water in hoth the Siuslaw River and its tributaries, as a residt of 

 which the clam beds were washed l)y c<M'nparativel}- fresh water 

 for nearlv four weeks. When examined at the end of January 

 1918. a ver\- high percentage of the young clams, then from 

 20 to 30 mm. in length, were dead. They were alive and in gc;od 

 condition when examined in December 1917 just before the 

 heavy rainfall. A dense layer of hue sand from 'j in. to 2 in. 

 deep covered the sur'face of the clam beds after the recession of 

 the high water, smothering, in my opinion, the }'ounger and weaker 

 individuals. Clams attaining a length of 50 mm. or more appar- 

 ently' were alile to withstand these unusual conditions and sur- 

 vived but practically all of the smaller individuals were <lestro\ed. 

 Beds of ^lya ai"enaria of considerable size are found in the 

 mud flats on the east side of Coos l*>ay opposite Xorth Uend. 

 from which source local markets are supplied. The species also 

 inhabits certain tide flats of the ^'aquina River above the town 

 of Yaquina several miles from the ocean, and has gained a foot- 

 hold in other bays and rivers along the northern half of the 

 Oregon coast. 



5. Saxidomtis giganteus Desha_\'es. 



Although this species has been taken at several points along 

 the Oregon coast and its shells may be found scattered along the 

 Ijeaches, it has accumulated in but one locality in sufficient num- 

 bers to be considered of economic importance. This clam is a 

 characteristic one of Netarts Ray where formerly it was recog- 

 nized as an abundant s])ecies (Figure I). Din-ing recent years. 

 however, a gradual depletion of the s]:»ecies has been going on. 



[lol 



