1882.] 
307 
[Hinckley. 
Prof. E. S. Morse described the differences he has found 
between the shells of the Kjoekenmoeddings of New England 
and those of the same species of molluscs living at the present 
day. Allied species are all found to vary in the same way, and 
farther, comparing the Japanese shell-heaps with those of New 
England, an exactly parallel state of things is found. Professor 
Morse illustrated these points by specimens and tables of measure- 
ments. 
Professor Hyatt observed that these changes of form could 
hardly be ascribed to the action of natural selection. Climatic 
influences seemed to be the only possible explanation. 
Mr. F. W. Putnam remarked that he had received specimens 
of Buccinum diversum from ancient mounds very much larger 
than the present forms of the same species. 
The following paper was read : 
ON SOME DIFFERENCES IN THE MOUTH STRUCTURE OF 
TADPOLES OF THE ANOUROUS BATRACHIANS FOUND 
IN MILTON, MASS. 
BY MARY H. HINCKLEY. 
The following observations on some of the differences in the 
external structure of the mouth of our tadpoles, were made at 
Milton, Mass. With the exception of Scaphiopus solitarius 
Holbr., the burrowing frog, the list includes all the species com- 
monly found in Massachusetts. 
Observing the mouth of these tadpoles, it will be seen that they 
are divided by differences m this organ into three groups ; 
that each one of these groups includes lesser differences of vary- 
ing importance ; and that, corresponding to these larval groups, 
differences of habit are found in the adult forms. 
Fig. 1 of Plate 5 represents the head of a full grown tad- 
pole of Rana catesbeiana, showing the position and relative 
size of the mouth. Between the flexible upper and under 
lip (fig. 2. a, b,) is a pair of hard, beak-like jaws, the margins of 
which are colored to a greater or less width with dark brown or 
