316 HYPEROODON. RYTINA. 



jaw, decays and softens away like the old cuticle of the sole of the 

 foot when steeped in water" (1). 



A thin transverse section of baleen, viewed with a low magni- 

 fying power, demonstrates that the coarse fibres, as they seem to 

 the naked eye, which form the central substance, are hollow tubes (2), 

 with concentric laminated walls. When a high magnifying power is 

 applied to such a section, the concentric lines are shown not to be 

 uniform; but interrupted here and there by minute elUptical dila- 

 tations, which are commonly more opake than the surrounding 

 substance, and which, like the calcigerous cells of true bone, are 

 probably remains of the primitive cells of the formative substance : 

 similar long elliptical opake bodies or cells, are dispersed irregularly 

 through the straight parallel fibres of the dense outer laminae of the 

 baleen plate. 



The chemical basis of baleen, according to Brande, is albumen 

 hardened by a small proportion of phosphate of lime. 



HYPEROODON. 



133. Before leaving the consideration of the horny teeth of 

 the Mammalia, it seems proper to notice in the present chapter the 

 hard horny pointed processes which are said to project from the 

 palate of the Bottle-nose Dolphin, thence called Hyperoodon, by 

 Lacepede ; which processes may be regarded as analogous to the 

 baleen-plates in true Whales, but I regret that no opportunity has 

 occurred to me of examining them. 



RYTINA. 



134. The singular armature of the palate and lower jaw, in 

 the Rytina, or Arctic Dugong, likewise falls within the present 

 category. According to Steller(3), this marine animal has no true 

 teeth, but only two large whitish dental masses, one adhering to 

 the palate, the other to the opposed part of the lower jaw : they 

 are not implanted by gomphosis, but adhere by numerous pores to 

 corresponding papillse of the membrane covering the palate and 

 lower jaw ; besides which, the palatal tooth is fixed at the sides of 



(1) Loc. cit. p. 397. (2) Heusinger Histologic, p. 198, pi. ii, fig. 3. 



(3) Nova. Comment. Petropolit. tcm. ii. p. 294, 1751. 



