REMARKS ON PETALODUS ALLEGHANIENSIS LEIDY. 
In an article entitled ‘Description of a New Species of 
Petalodus,” etc: (this) JourNAL, Wel, Ill No, 5) Diy Ora tay, 
describes an interesting specimen of a selachian tooth from the 
Carboniferous limestone of Illinois, for which he proposes the 
name Petalodus securiger. A number of characters are enumer- 
ated, in which the supposed new species is believed to differ 
from P. alleghamensis and P: destructor, these two being regarded 
by the author as distinct. The article concludes with the sug- 
gestion that in case the identity of P. alleghaniensis, destructor and 
securiger ultimately be established, the name P. ofzoensis, proposed 
by Professor J. M. Safford in 1853, should be reinstated on the 
ground of priority. 
In the opinion of the present writer, all the forms described 
under the above names are identical, and as the validity of the 
well established title proposed by Leidy is brought into question, 
a few considerations may not be out of place in favor of its 
retention. These considerations would have been submitted 
much earlier, but for the fact that the writer has been awaiting 
an opportunity for comparing the Illinois specimen with the fine 
series of Petalodont teeth in the collection of the Museum of 
Comparative Zoédlogy at Cambridge; he regrets, however, that a 
reported accident to the specimen has rendered it inaccessible to 
him. 
As Dr. Hay does not state his reasons for preferring to 
regard P. alleghaniensis and P. destructor as distinct species, it 
may be as well to accept the opinion of Leidy, Newberry, St. 
John and others as authoritative, who hold that the two names 
are synonymous. In point of fact, less differences are to be 
noticed between specimens attributed to the above-named species 
than are exhibited by the teeth of the one species P. acuminatus 
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