162 BIOLOGICAL SURVEY OF 



The Ledidae are another common form and are represented 

 by four species, with Yoldia sapotilla the most prominent. 

 They occur in large numbers, particularly Y. sapotilla, and 

 undoubtedly are one of the most valuable of fish foods that the 

 waters afford. They are found everywhere that any kind of 

 mud bottom occurs, whether it be on the large patches of 

 mud bottom or among the rocks where deposits of mud have 

 lodged and the animal can find a foothold. 



The average length dredged is a scant inch and large species 

 are rarely met with, proving that they do not acquire much 

 growth before being eaten. This is borne out by the fact that 

 very few large dead valves are dredged, and also that large 

 specimens may be dredged back in the estuaries. The codfish 

 enter the inner Bay in the cold months and cruise over its 

 bottom until May and sometimes beyond, but they do not go 

 into the estuaries, and therefore these forms are given an 

 opportunity to acquire their full size. 



The Pectinidae give us two species, one of them the giant 

 scollop of commerce. These bed very hard here and it takes 

 considerable effort to get them up. They used to be very 

 numerous, but the recent fishing has kept them down. A 

 favorite spot was the Western Bay and Blue Hill Bay, and 

 they must have been very abundant years ago, for I have 

 found large masses of shells carefully stacked up in lots of 

 10 or more cubic feet, now covered by a foot or more or soil 

 and moss and growing trees a foot in diameter. 



Mytilus edulis is, of course, everywhere throughout this 

 Region. On the piles, rocks, or wherever it can attach itself, 

 and also forms large beds in the flats, acres in extent. Modi- 

 olus modiolus is also distributed. They are the chief Mytili- 

 dae, which give us eight species, but mention must be made of 

 Crenella, which is common. 



The Astartidae occur generally and in five species, with 

 Astarte undata the very common form, and the beautiful 

 A. castanea scarce. 



Of the Carditae, Venericardia borealis has a general occur- 

 rence with V. novangliae, more plentiful in the southeastern 

 part of the Region than elsewhere. 



