Iviii. PRESIDENT'S ADDRESS. 



Accipenser and Scaphirhynchus arc now living in the Northern 

 Hemisphere ; and frequent the mouths of the rivers of Europe, 

 Asia, and North America. Of Scaphirhynchus four species are 

 known, one from the regions of the Mississippi, and three from 

 Central Asia. Their appearance in regions so widely distant is 

 a striking instance of the affinity of their fauna. The skull is 

 cartilaginous, preserving the typical form, and is overlain with a 

 series of dermal-bones. The notochord is persistent. The 

 neural- and haemal-arches are either cartilaginous or bony ; the 

 tail is heterocercal. The skin is naked, dotted over with bony- 

 scutes, or covered with rhomboidal-scales. They are not found 

 in beds earlier than the Eocene Age. Mr. A. Smith Woodward 

 remarks that the typical forms of this sub-Order constitute a 

 link, connecting the cartilaginous Ganoids with the Tdeostei, 

 whose bones are fully developed. The well-known typical 

 Sturgeon is a freshwater fish, characterised by its elongated 

 body, produced snout, and the toothless jaws of the adult. It 

 swims low, and grovels along the bottom, feeding in shoals on 

 decomposing animal and vegetable substances carried down by 

 the rivers with the debris of the continents through which 

 they pass. The sides and middle parts of the body are 

 protected by regularly arranged dermal-plates. This protection 

 renders the ossification of the endo-skeleton needless. The 

 exo-skeleton, which is relieved from much of its weight by the 

 detached instead of converted dermal-plates, is further aided by 

 a large air-bladder, by which it can with the greater facility rise 

 to the surface. These plates afford an insight into the habits 

 and conditions of the heavily protected Ganoids, so abundant 

 in the early periods of the earth's history. 



Pycnodontidae. This family ranges from the Lias to the 

 Eocene Age. We have records of it in Europe, Asia Minor, 

 North America, and Australia. Their bodies are much com- 

 pressed, like the John Dory, and covered with large rhomboidal, 

 enamelled scales. The notochord is persistent, and the neural- 

 arches and ribs are entirely ossified. The maxillae are toothless, 

 the palate carries five longitudinal rows of oval or round teeth ; 



