Mollusc Shells 

 Example 1. — Fresh -water TflusHel (UnioSp. ov Anodonta i^.) 



Material. — Mussels may be found in rivers, ponds, 

 and lakes throughout the country. If more convenient, 

 clams may be used. These may be had from fish-deal- 

 ers and restaurants everywhere. The shells may be pre- 

 served dry or in alcohol. For their study the stu- 

 dent will need nothing but a dish of water, some dilute 

 hydrochloric acid, a hand-lens, and a test-tube or tum- 

 bler. 



Oyster -shells will be especially interesting for com- 

 parison. 



Method of Examination. — Kemove the animal from 

 its shell, noting carefully the points where the connec- 

 tion between the shell and soft parts is closest. If, as 

 will be the case with the living animal, the shell should 

 be difficult to open, place it in warm but not boiling 

 water for a few minutes. Before studying the other 

 structural features, put some of the shells, if dry, into 

 water to soften the hinge-ligament, and some pieces 

 into the dilute hydrochloric acid in a test-tube or tum- 

 bler. 



MOEPHOLOGT 



a. The entire shell. — What is its shape ? Where are the 

 points of its greatest length, breadth, and thick- 



