344 NEW-YORK FAUNA. 



SUB-CLASS II. CARTILAGINOUS FISHES. 



Bones cartilaginous. Cranium divided hi/ indistinct sutures. Gills generally fixed ; the 

 membrane without rays. Maxillary and intermaxillary hones cither wanting or rudi- 

 mentary, the palatines or vomer alone supplying their place. 



Obs. The fishes of this sub-class form a small group, neither superior nor inferior to the 

 others, but form with them a parallel series. The skeleton contains no bony fibres, but cal- 

 careous grains. The gelatinous substance, which in other fishes fills the intervals of the 

 vertebras, and communicates from one to the other only by a small hole, forms in several genera 

 a continuous cord which perforates them all. . 



ORDER I. ELEUTHEROPOMI. 



Gills pectinated, free as in ordinary fishes, with one large external aperture on each side, 

 furnished with a strong opercle ; without rays. Upper jaw formed hy the palatine hone, 

 firmly united to the maxillary ; intermaxillary rudimentary. 



FAMILY STURIONID^. 



Body elongated, with large osseous plates or tubercles arranged in longitudinal rows. Mouth 

 placed beneath, very protractile, and without teeth. 



Obs. a small group, containing at present about fifteen species, but not thoroughly examined. 



GENUS ACIPENSER. Linneus. 



Snout prominent ; nostrils and eyes lateral. Four pendent barbels on the under side of the 

 snout. Air-bladder large, and communicating hy a large hole with the stomach. Dorsal 

 and anal on the posterior p)art of the body. 



THE LAKE STURGEON. 



ACIPENSER RTJBICCNDUS. 



PLATE LVin. FIG. 191. 



Acipcnser nibkundus. Lesueur, Trans. Am. Phil. Soc. New series, Vol. 1, p. 388, pi. 12. 

 A. id., The Ruddy Sturgeon. Richardson, Faun. Bor. Am. Vol. 3, p. 284, 

 A. id. KiRTLAND, Report on the Zoology of Ohio, p. 196. 



Characteristics. Body of a ruddy hue. Head flat between the eyes. Lateral series lozenge- 

 shaped, oblique, and thirty-nine in number. Length four feet. 



