12 physad^e. 



It results from these facts, that Cuvier and 

 Ferussac were wrong in naming this family 

 Pulmonifera and Pulmonalia; and I believe we 

 are indebted to Lamarck, for having been the 

 first to indicate the respiratory organs as true 

 branchiae in structure, but adapted to aerial 

 respiration.* 



The North American Limneans may be said 

 to range from the thirty-fifth to the fiftieth de- 

 gree of north latitude; but some are found 

 farther south, Limnea attenuata inhabiting near 

 the city of Mexico; and a species of Physa, and 

 one of Planorbis, near Vera Cruz. A larger 

 number of species inhabits New England than 

 any other part of North America of equal extent; 

 whilst not a single species of the Melanians, 



own, rather than in a public conveyance, as affording better 

 facilities for observation. In the summer of 1841, ac- 

 companied by an assistant, and having about one hundred 

 and fifty pounds additional weight, I drove a single horse, 

 still in my possession, the distance of 1800 miles in forty- 

 five consecutive days, and often over mountainous regions, 

 and the most execrable roads, frequently breaking shafts, 

 springs, and other portions of the vehicle, and examining 

 every stream upon the route. 



* Blainville and Deshayes appear to hold the same opi- 

 nion. 



