1054 
SCANDINAVIAN FISHES. 
that of a respiratory organ. It is a relic of the seg- 
mental organs found in lower animals, and recurs in the 
Selachians and "Ganoids, as well as in the Salmonoids, 
Enchelymorphs, and Mormyroids among the Teleosts. 
fhe family of the Sturgeon-fishes contains only 
two, not very dissimilar genera, S c a p hirhynchops and 
Acipenser. The former, of which only one species is 
known, with spatulate snout, long but shallow (depressed) 
peduncle of the tail, with the upper lobe of the caudal 
fin prolongated into a filamentous appendage, and further 
characterized by the absence of spiracles, belongs ex- 
clusively to the southern regions of North America. 
Genus ACIPENSER. 
Peduncle of the tail terete (not depressed ) and at least 
meet from each 
The Sturgeons have met with the same variety of 
systematic treatment as the Salmons, and probably from 
the same cause. They are anadromous fishes, breeding 
in fresh water — a few, it is true, permanent inhabitants 
thereof — but else living in the sea. Their geographical 
range is about the same as that of the Salmons, ex- 
tensive enough to offer a great variety of physical 
environments. They also show an inconstancy of form 
fully comparable with that of the Salmons, and the 
methods of their classification have been equally diver- 
sified. In 1870 Dumeril described" 81 species of this 
genus, among them 62 from America. In the same 
year Gunther adopted in his Catalogue only 19 spe- 
cies, 9 American. Jordan and Gilbert 6 (1883) re- 
cognised only 5 species in America, 2 from the Pacific 
coast, 3 from the Atlantic; but the specific rank even 
of these may be called in question. 
The characters hitherto employed in the definition 
of the species are subject to considerable variations. 
It has long been known that the large body bucklers 
of young Sturgeons are set closer together, and have 
a longer, more pointed, and usually more hooked, cen- 
tral spine, than those of older specimens. Their num- 
ber was indeed recognised by Gunther as a valid 
character, but varies in the common West European 
and American Sturgeon, for example, between 11 and 
13 in the dorsal row and between 26 and 34 in the 
upper lateral row. According to Jordan and Gilbert 
these variations extend between 11 and 14 in the 
twice as deep as the lateral caudal plates , which do not 
side of the body. 
dorsal row and between 27 and 36 in the upper lateral 
rows, according to Kroyer between 10 and 14 in the 
former and between 26 and 31 in the latter. Fatio c 
counted 15 plates in the dorsal row. Of the small 
plates in the skin between the large bucklers Gunther 
remarks, in the case of the common Sturgeon, that in 
very young examples (which thus would be referred 
to the genus Huso of Dumeril) the skin is provided 
with very small rough points; in older ones these ossi- 
fications are broader, rough, substellate, and more (as 
in the genus Acipenser of Dumeril) or less (as in An- 
taceus of Dumeril) regularly arranged in oblique se- 
ries d . According to Milner’s observations e of the 
American fresh-water Sturgeon, the large bucklers in- 
crease in size until the fish has attained a length of 
about 63 or 64 cm., but afterwards diminish, partly 
owing to the detrition of the spines, partly by resorp- 
tion of their margins, and both at the dorsal line and 
the ventral margins they partially drop off, or at least 
become indistinct. Simultaneously with this process 
may be observed a shortening of the snout; and the 
far greater relative length of the snout and its more 
pointed form in young Sturgeons give the head an 
appearance quite different from that of older specimens. 
The external sexual characters are not marked, 
and but little has been observed on this head. In the 
Seuruga (Slier g, Acipenser stellatus ) of the Black Sea and 
its feeders, which species is characterized by a very long 
and slender snout, the females, according to Heckel 
a Nouv. suites a Buffon , Hist. Nat. Poiss., tome II, pp. 87 cett., 
b Bull. U. S. Nat. Mus., No. 16, pp. 85, cett. 
c Fne Vert. Suisse , vol. V, part. II, p. 491. 
d The same observation had already been made by Nilsson ( Skand . Fna, Fisk., p. 
systematic significance. 
c U. S. Comm. Fish and Fisher., Rep., part. II (1872 and 1873), p. 70. 
702), though he did not expressly point out its 
