THE STURGEON TRIBE 2889 



adult; the heterocercal tail; and by the skin being either naked or with some scales 

 on the upper lobe of the tail. The first of the two existing genera is represented 

 by the spoon-beaked sturgeon {Polyodon folius} of the Mississippi, which grows to a 

 length of six feet, and is characterized by the production of the upper jaw into a 

 very long spoon-like beak, with thin, flexible margins, equal to one-fourth the total 

 length in the adult, but still longer in the young. The gill cover ends in a long 

 tapering flap; the upper lobe of the tail bears a numerous series of narrow fulcra; 

 and the air bladder is cellular. On the other hand, the slender-beaked sturgeon 

 {Psephurus gladius} from the Yang-tse-kiang and Hoangho rivers of China, differs 

 in the more conical form of the beak, and in the large size and small number of the 

 caudal fulcra. Growing to an enormous length it is said as much as twenty feet 

 this fish agrees with the preceding in the very small size of its eyes, from which 

 it may be inferred that both seek their prey without depending upon sight. 

 Indeed, in the muddy waters of the rivers they inhabit, eyes can be of little use, 

 and it has been suggested that these fish depend chiefly upon their beak, which is 

 probably employed as an organ of touch. The flesh of both species is eaten. 

 Among several fossil forms, we may mention the genus Crossopholis , of the North- 

 American Eocene, on account of the retention of a series of oblique rows of scales 

 on the upper lobe of the tail, as we thus have evidence of the descent of the family 

 from fully scaled fishes. 



From the preceding family the typical sturgeons (Aripenserida') 

 Sturgeons may ^ e distinguished by the absence of teeth in the adult, and the 

 presence of five longitudinal rows of bony plates on the naked body, 

 which is elongate and subcylindrical in form, as well as by the presence of four bar- 

 bels in a transverse line on the under surface of the muzzle. The muzzle is some- 

 what produced, and either subspatulate or conical in form, with the small, 

 transverse mouth on its lower surface. All the vertical fins are armed with a single 

 series of fulcra on their front edges; the dorsal and anal are situated at a moderate 

 distance from the caudal; and the large air bladder is simple. Confined to the 

 temperate regions of the Northern Hemisphere, sturgeons are either exclusively or 

 partially fresh-water fish, some of them only ascending rivers for the purpose of 

 spawning, after which they return to the sea. With the slender-beaked sturgeon, 

 they include the largest fresh-water fishes of this region, several of the species 

 commonly growing to ten feet, while some are much larger. The females deposit 

 enormous numbers of extremely minute eggs, the product of a single individual 

 having been estimated at upward of three millions during a season. This wonder- 

 ful fecundity easily accounts for the enormous numbers in which sturgeon, in spite 

 of constant persecution, still crowd the northern rivers during the spawning season. 

 In addition to the excellence of their flesh, sturgeon are valued for their roe, from 

 which is manufactured caviare, and for their air bladder, the inner coat of which 

 forms the basis of isinglass. In a fossil state sturgeons are unknown before the 

 upper part of the Eocene period. All the members of the genus are exceedingly 

 voracious fishes, and the majority are mainly carnivorous. During the winter many 

 or all of them crowd together, either in inlets of the sea, estuaries, or the deep 

 pools of rivers, where they undergo a kind of hibernation; and it is stated that in 



