70 



PYCNODONTS. 



less constricted at their base, and supported on a short pedicle, which 

 is anchylosed to the osseous substance of the jaws. (PL 30, fig. 1). 

 The detached hemispherical teeth of the Lepidoid fishes are so like 

 those of some of the genera of the Pycnodont family, as to be scarcely 

 distinguishable. 



The only difference which M. Agassiz recognizes between 

 the teeth of Lepidotus and those of Sph(srodus is, that in the former 

 they have a slight constriction at the base of the enamel. But having 

 ascertained this character not to be constant, I submitted the teeth of 

 the Lepidotus Mantellii to microscopic examination, and have compared 

 their intimate texture with that of the similarly shaped teeth oiSpharo- 

 dus Bucklandi. The dense substance of the tooth of the Lepidotus (PI. 

 31) is composed of fasciculate tubes continued directly from the cells 

 of the osseous base, radiating, with a direction vertical to the surface 

 of the tooth, and giving off branches, at an acute angle, from their 

 very commencement ; thus far the general character of the texture of 

 the tooth is the same as that of Sphcsrodus, afterwards to be described ; 

 but the fine branches into which the fasciculate tubes resolve them- 

 selves in Lepidotus, diverge at a much more open angle from the main 

 trunk, are spread out more widely, are more curved, and pre- 

 sent the appearance of the stems of corn beaten down with heavy rain. 

 These fine terminal branches are inextricably interwoven, and present 

 the appearance of numerous anastomoses, but do not form so dense a 

 plexus of calcigerous tubes and cells as in the teeth of Sphcsrodus in 

 which the corresponding tubes and cells intercept the light. 



PYCNOr)ONTS.(l) 



28. In this family of fishes, of which all the representatives 

 are extinct, the teeth present a greater diversity of character, and 

 a higher degree of development than in the preceding ; the preva- 

 lent form approaches to that of the Lepidotus ; the teeth being generally 

 adapted for crushing, and having a smooth convex or flattened crown. 

 In some genera they attain a very large size ; when smaller they are 

 arranged in several rows. They have been observed in the intermax- 

 illary, premandibular, palatine and vomerine bones. 



(1) nvKvoQ^ thick, cSovg^ a. tooth; thick-toothed fishes. 



