11 



[Communicatea May Sth, I860.] 



Sir. Lea mentioned that he had recently received a letter from Dr. Showalter 

 of Uniontown, Alabama, in which he mentions that specimens of Physa (gyrina) 

 Say, which he sent on, were obtained in an open neglected cistern, and in a 

 trough of water supplied by an Artesian well ten miles from the town. Dr. S. 

 expressed his surprise that these Physa should find their homes so soon at these 

 Artesian wells. There are no streams or pools near to these wells, but in a few 

 years after they are bored and water supplied, these shells may with certainty 

 be found. Mr. Lea went on to mention that he had nearly 30 years ago found 

 an undescribed species of Lymnma, accompained by Physa helerostropha, Say, in 

 a small artificial pond on the high grounds near to the Falls of Schuylkill, 

 about four miles north of Market Street, now within the limits of this City. He 

 published an account of it in April 1834, in the Trans. Am. Phil. Soc. under 

 the. name of acuta. The pond was small and dug out for 1J to 2 feet deep, 

 simply for the supply of rain water for cattle. Afterwards it dried up and the 

 shells were no longer to be obtained there. He never found this Lymnoea in, 

 any other habitat ; but many years subsequently, Dr. Ingalls, of Greenwich, 

 X. Y.. near to Lake Champlain, sent him several specimens of what he regard- 

 ed as a new Lymnaia, but which was at once recognised as the acuta, heretofore 

 r'onnd only in the one habitat near the Falls of Schuylkill. In the minds of 

 some zoologists a difiiculty exists as to existence of species in such constricted, 

 isolated points as mentioned above, but that difficulty in Mr. Lea's mind was 

 done away with under the belief that very young molluscs may be transported 

 on the feet of birds from distant points, or on those of cattle going to drink from 

 one place to another. The idea of spontaneous generation could not of roarpe 

 be for one moment admitted. 



