TO 



ISAAC HAYS, M.D., 



LATE PRESIDENT OF THE ACADEMY OP NATURAL SCIENCES. ETC. 



My very dear Friend: — 



I have already dedicated one of my volumes of Observations on the Genus 

 Unio to you; still, as this is the most important of all my works, I cannot resist 

 the inclination to offer it to you, who have been my lifelong companion, associate, 

 and friend. For over fifty years we have been united in labors to promote the cause 

 of Science, by the ties of friendship and the congeniality of tastes and pursuits. In 

 my particular branch you have alwa} r s aided me by your sympathy and advice. All 

 medical men know what eminent services you have rendered in the advancement of 

 the healing art. These are claims which induce me to ask you to accept this, the 

 fourth edition of my Synopsis, which is almost a new work. 



Always your constant and sincere friend, 



ISAAC LEA. 



