264 



ZOOLOGY 



and four years they are ready for the market. Sometimes oysters 

 are artificially fattened by placing them on beds near the mouths 

 of fresh water streams. Too often these streams are the bearers 

 of much sewage, and the oyster, which lives on microscopic 

 organisms, takes in a number of bacteria with other food. Thus 

 a person might become infected with the typhoid bacillus by eat- 

 ing raw oysters. 



The oyster industry is one of the most profitable of our fisher- 

 ies. Nearly $30,000,000 a year has been derived during' the last 

 decade from such sources. Hundreds of boats and thousands of 

 men are engaged in dredging for oysters. Some of the most 

 important of our oyster grounds are Long Island Sound and 

 Chesapeake Bay. 



Clams. — Other bivalve mollusks used for food are clams and 

 scallops. Two species of the former are known to New Yorkers, 



one as the '' round," 

 another as the '' long " 

 or '' soft -shelled " 

 clams. The former 

 ( Venus Merceneria) 

 was called by the In- 

 dians quahog, and is 

 still so called in the 

 Eastern States. The 

 blue area of its shell 

 was used by the In- 

 dians as wampum, or 

 money. The quahog 

 is now extensively used 

 as food. The " long " 

 clam (Mya arenaria) 

 is considered better 

 eating by the inhabit- 

 ants of Massachusetts 

 and Rhode Island. This clam was highly prized as food by 

 the Indians. The long siphon, incorrectly called neck, enables 

 these clams to burrow deep into the mud and yet take food and 



Round clam {Venus Merceneria); A. A.M., anterior ad- 

 ductor muscle; A.R.M., anterior retractor muscle; 

 P.A.M., posterior adductor muscle; P.R.M., posterior 

 retractor muscle; F., foot; C, cloacal chamber; I.S., in- 

 current siphon; F.S., excurrent siphon; EO., heart; 

 G., gills; M., mantle; Z).GL., digestive glands; S., 

 stomach; /., intestine; P., palp; R., posterior end of 

 digestive tract. 



