88 SQUALID.E. 



The correctness of this popular view is amply confirmed by the re- 

 searches of the anatomist and physiologist. Aristotle was the first of these 

 to fix this idea scientifically ; and to establish the tribe of ra aikajri upon 

 the cartilaginous nature of the bones, and the supposed universal vivi- 

 parous production of the young.* 



The Sharks in common with the Skates or Rays (Raiid^), the Stur- 

 geons (Sturionida:), and the Lampreys (Petiomi/zida), forming together 

 the series termed by Cuvier Chondropterygianse (from %ov^^o?, cartilage), 

 are in fact distinguished from the generality of the true fishes by the cartila- 

 ginous instead of bony structure of their skeleton ; the parts of which are 

 not composed of bony fibres, but of an aggregate of granular calcareous par- 

 ticles, effacing more or less the joints, divisions of the bones, and more 

 especially the sutures of the skull. Considering the class, with Cuvier, rather 

 in the light of a series parallel with the true fishes, than as either of a sub- 

 ordinate, or of a higher rank ; for if on one side they degenerate towards the 

 Invertebrata, on the other they approximate in certain points of structure to 

 the Reptilia ; a curious analogy in outward form and certain characters 

 may be traced out between the families or groups of each respective line. 

 Thus in the Chondropterygian Series, or their confines, 



Sharks = Scombridas. 



Skates and Rays = Pleuronectidae. 



Lampreys = Mursenidre or GobidjE, or Cyclopteridae. 



Sturgeons = Syngnathidse, or Balistidffi. 



Balistidse and Diodontidje = Lophidte, in the series of the true fishes. 



The Sturgeons and the Lampreys agree in this — that they deposit eggs 

 or spawn like the true fishes : but the Sturgeons have the gills or branchise 

 free, opening by a single orifice, and covered by an opercle : whilst in the 

 Lampreys the respiratory organs are a row of mere cells, each opening 

 either directly by a distinct orifice on the sides of the neck externally, or 

 into an internal common tube or channel ; and the spine is reduced to the 

 lowest state of developement, marking the passage from one great division of 

 the animal kingdom (Verttbrata), to the other (Invertebrata or Mol- 

 lusca). But in the Sharks and Rays, the spine, though cartilaginous, is 

 perfectly continuous and distinct ; the branchite, as in the sturgeon or the 

 ordinary fishes, are composed of pectinated laminae, which are not however 

 free, and opening by a single orifice, but fixed or adherent by their outer 

 edge to the integument or skin, and opening on both sides of the neck 

 by as many separate external orifices as there are intervals between each 

 pair ; the rays of the fins are indistinguishable : and lastly, many of the 

 species are, as Aristotle thought of all, viviparous ; although others, and 



* Confer Anst. Hist. (Schneideri) A. S, r. «. 13, ?. (i, and n. 



