20 CYCLOSTOMES. 



CHAPTER 11. 



TEETH OF CYCLOSTOMES. 



MYXINES. 



10. In the class of fishes, as in that of reptiles and mammalia, there 

 are species which are wholly destitute of teeth. These edentulous 

 fishes are most common in the cartilaginous division of the class. 

 The sand-prides {Ammocetes), the sturgeons (Acipenser), the paddle- 

 fishes fPlanirostra and Aodon), are examples. The whole order of 

 Lophohranchii of Cuvier, which includes the pipe-fishes (Syngnathus) , 

 and the Hippocampus, is edentulous. 



The lowest organized fishes with worm-like bodies and parasitic 

 habits, as the mj^xinoids and lampreys, are also destitute of true 

 calcified teeth, but have them replaced by horny substances of a 

 conical, sharp-pointed, and often slightly recurved form, resembling 

 the teeth of the entozoa, the habits of which these suctorious fishes 

 simulate. The hag-fish {Myxine glutinosa) , and other cognate species 

 now grouped together by Miiller under the genus Bdellostoma , have 

 a single tooth on the median line of the palate, and a double serrated 

 horny plate on each side of the upper surface of the tongue. The 

 palatal tooth(l) is moderately long, conical, and recurved, with a tumid 

 margin around its base, which is hollow, and supported upon a conical 

 pulp, firmly attached to a fibro-cartilaginous plate,(2) situated beneath 

 the anterior commissure of the palatal cartilage. The basal-plate 

 of this tooth is further attached by ligaments, the anterior of w^hich 

 passes to the hinder part of the rostral cartilage, and the posterior 

 one to a cavity at the commissure of the marginal palatal cartilage. 



The lingual dental plates(3) are four in number, two on each side, 

 of a curved form, hollow at the base, and implanted, like the palatal 

 tooth, on a reproductive pulp of a corresponding form. (4) This pulp, 

 and the margin of the base of the dental plates are attached to the 

 perichondrium of the lingual cartilage. The dentations of these 

 lingual plates are conical, sub-compressed, sharp-pointed, with the 



(1) PL 2, fig. 1, b. (2) ib. a. (3) ib. fig. 2, 6. (4) ib. fig. 3, a. 



