LT ELS 
AMERICAN NATURALIST. 
Vol. VIII.— MARCH, 1874.— No. 3. 
THREE DIFFERENT MODES OF TEETHING AMONG 
SELACHIANS.* 
3 F » 
Ae . BY PROFESSOR LOUIS AGASSIZ. 
Axovt two years ago Mr. Orestes St. John came to the Mu- 
seum of Comparative Zoology with a very large collection of fossil 
fish teeth, with the intention of identifying them and comparing 
them with those which we had in our own collections. This 
came an occasion for me to look over the materials we possess 
In former years Į had paid considerable attention to the subject 
and contributed somewhat to the advancement of our knowl- 
edge in respect to the peculiarities of teeth among the representa- 
“tives of the class of Selachians. I soon found that the progress 
of paleontology and zoology made the present materials on hand 
quite insufficient for the task. It was not known how constant 
-the characters derived from the teeth among § Selachians could be 
considered to be, or, with few exceptions, what changes took 
place with age. So I determined upon the voyage of the Hassler 
~ *This paper is: printed from a , repòrt taken of Professor Agassiz’ rpn 
before the “ National Academy of: Scien ov. 20, 1872 
‘It was the intention of the author €o revise the report for publication in the NATU- 
, and he to do so, the first four pages of the manuscript having 
Ween c corrected during the last two w weeks that Says at hirs museum. The 
s of the lamented author, and 
pave made 1 seed and 
of must be remembered that he would | esse ets h i1 
; labors, — Eps. 
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