46 Lessons in Zoology. 



Lesson III. 



The last two leaaona shonld be thoronghly reviewed by the aid of 

 the shells and a blackboard sketoh on which the organs can be 

 located aa they are described by the children. 



It will add interest to the talk abont the borrowing habits oi the 



dam, if the teacher can show 



iSMlil^^^ft^ tc- * razor -shell (Fig. 6), and 



explain that this kind of clam 



'"*■ ^' burrows so fast with its pnw- 



erfal foot that one can head it off only by <> andden obliqne ont 



with the spade. 



Sooth of New York the 

 round clam, or qaahog 

 (Fig. 7), ia the common 

 one in the market, and 

 will be the most conven- 

 ient type for theae lea- 

 Bona. On sandy shores 

 this barrows bnt little be- 

 low the snrface, often even 

 crawling abont with its 



shell partly exposed. This habit is the explanation of the short 

 siphon tabes. It ia taken in mnddy creeks by long tongs or rakes. 



The large, rounded shell of this clam, with its prom- 

 inent beak, has the hinge ligament on the outside. Chil- 

 dren will see, by carefully opening and shutting it, that 

 the ligament is stretched when the shell is closed, and so 

 opens the shell when it contracts to its natural size. 



The foot and mantle edges are white, the siphon tubes 

 yellowish or brownish orange, mottled toward the end with 

 dark brown or opaque white, and are separated a little at 

 the end. The mantle lobes are separate and ruffled at 

 the edges. The elam easily burrows when necessary, by 

 means of its large foot with a broad, thin edge, which can 



