TEETH or FISHES. 



309 



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fig'. 250, c, opposed to two dentigerous pharyngeal jaws, d, d, 

 below. Ill the Lcpidosircu a single maxilhuy dental plale, 

 hg. 251, II, is o]i[)osed to a single mandibular one, h, and there are 

 two small dentieles on the nasal bone, c. In the extinet Sharks 

 with crushing teeth, called Ceratudus and Ctenodus, the jaws were 

 armed with four teeth, two above and 217 



two below.' In the Chim;\;r;c two £s:y<;rS^\ 



mandibular teeth are opposeil to four . ^ 



maxillary teetli.^ From this low point 

 the number in ditferent Fishes is })ro- 

 gressively multiplied until, in the 

 Pike, the Siluroids, fig. 252, and many 

 other fishes, the mouth becomes 

 crowded with innmnerable teeth. 



With respect to form, I may pre- 

 mise that as organised beings with- 

 draw tliemselves UKH'e and more, in 

 their ascent in the scale of life, from 

 the influence of common physical 

 agents, so their parts progressively 

 deviate from geometrical figures : it 

 is only, therefore, in the lowest ver- 

 tebrated class that we find teeth in the 

 f(.)rm of perfect cubes, and of j)rlsms 

 or jilates with three sides (^Blijlcfes), four sides ( Scancs), five, or six 

 sides (^MijUohutcs, fig. 249). The cone is the most connnon form in 

 Fishes: such teeth may be slender, sharj)- ojg 



pointed, and so minute, numerous, and closely 

 aggregated, as to resemble the plush or pile 

 of A'eh'ct ; these are called ' villifbrm teeth ' 

 (di'/ifes villiformes, dents en velours^); all the 

 teeth of the Perch arc of this kind : when the 

 teeth are equally fine and numerous, but 

 longer, they are called ' ciliiform ' {denies 

 ciliifunnes) : when the teeth are similar t<^, but t "' ^ ^' ' "^^f 

 rather stronger than these, they are called ' setiform ' (denfes siii- 

 fornies, dents en hroase) : conical teeth, as close set and sharp 

 pointed as the villiform teeth, but of larger size, are called ' rasp- 

 teeth ' (dentes riiduliformes, dents en I'ape or en cardes, fig. 252 ) ; 

 the Pike presents such teeth on the back part of the vomer : tlie 

 teeth of tlie Sheat-fish {Silurus glanis) jiresent all the gradations 



' Y. pi. 22. = V. fil, 28. 



' The French terms are those us&l l>y Ciivicr in xxiii. passim. 



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octiou i>f 1,1. nth Of Onjdcrojiii!' 

 mayn. v. 



