242 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
or less unreliable and transient characters, as is proved by the fact that upward of 
forty American species have been discovered by this reckless author amongst the ma- 
terials preserved in the Museum d’Histoire ISTaturelle at Paris. The actual number of 
American species of sturgeons is seven, according to Jordan and Gilbert (Synopsis 
Fishes, N. Am., p. 85), and probably even less according to these authors. The fictitious 
species, A. oxyrhynchics, has clearly been based for the most part upon the young 
of A. stiirio, as is shown by some of the reputed figures of the former. Eeferriug to 
the original description by Mitchill of A. oocyrkynehns, it is clear from a letter which he ^ ,1 
quotes from a Mr. De Witt, that then, as now, it was supposed by some of the fisher- 
men that the sharp-nosed, small sturgeons were a distinct species. This belief is I 
widely prevalent amongst the sturgeon fishermen of the Delaware River, where the ■< ; 
young animal is popularly known as the “Mamoose,” probably an Indian name, as ■ 
I hear from my friend Mr. John Ford. i i 
It argues very unfavorably for the sagacity of Mitchill that he should have omitted , I 
to note that in the young, sharp-nosed forms, the roe is never developed to maturity. ■ I 
Only one large example of the long-snouted form amongst hundreds of specimens of < I 
A. ftturio has fallen under my observation, and this specimen did not appear to me to I I 
be essentially different from the usual blunt-nosed adult form, except in a proportion- ; 
ally longer snout. Further observation also showed that no two individuals presented ■ : 
exactly the same form and proportions of the snout and head ; it is therefore clear that i ! 
the Acipenseridce are variable to a high degree, and that the selection of a marked vari- 
ation as the tyi^e of a distinct species, without the study of a great many specimens, : I 
is to say the least, a very unscientific proceeding. The extreme rarity of adult 
instances of this variation is further proof that it is scarcely fair to consider it a sub- ; ; 
species, especially since it is known that such individuals are taken in association with ; ; 
the usual form of A. sturio. 
A careful study of the dermal plates of the young of A. sturio shows that they f 
increase in breadth and length in the course of further growth, to some extent, at least, - 
by the fusion of the basal plates of the dermal denticles to their edges. This is also * j 
very evidently shown by their greater height as compared with their breadth in still f ; 
younger specimens, as shown by the illustrations of the very young of A. huso given 
by Brandt and Ratzeburg. This method of their growth is continued until the dermal ' 
plates measure 3 or 4 inches across, so that as a result the growth in length and ^ 
breadth is much more rapid than their growth in height. This method of growth 
also serves to explain in what manner the distinction between the opisthoceutrous ■ 
and mesocentrous plates arises; as a consequence, it is easy to see that there can be • 
no hard and fast line between the one and the other form, both being merely younger , j 
and older stages of the development of the dermal plates. 
This conclusion may be still further fortified by the circumstance that it is only the 
species which are smallest that are markedly opisthoceutrous, while the larger are ■ 
mesocentrous, as shown by DumeriPs own comparisons. ( 
Of what value such characters are in classification may safely be left to those who ; 
have the proper morphological training to use them with discrimination. That these ; 
characters have not been used with discrimination is shown by the remark (Jordan 
and Gilbert, Synopsis Fishes, N. Am., p. 85), that “ the same species at different ages 
may frequently belong to two or more of these subgenera,” meaning those proposed ■ 
by Dum^ril. 
