HOW THEY MAY BE LOST. 101 



which it succeeds, and it frequently expels at the same 

 time the supplementary molar; so that if forty-four 

 teeth be developed in the male horse, it is very rare 

 that they are all present at the same time." 



That Kemnant teeth are usually regarded as phe- 

 nomena is abundantly proved by some of the ex- 

 tracts that follow. In "Johnson's New Universal 

 Cyclopedia" (p. 995), article "Horse," it is said: 



"An additional small tooth is occasionally found in 

 advance of the upper molar series. This tooth, when 

 present, is the smallest of all the teeth, and, as it has 

 neither predecessor nor successor, its nature is in 

 doubt." 



As the nature of these teeth appeared to be clearly 

 explained in the article " Horse, Fossil," which imme- 

 diately follows that on the " Horse," I wrote to Prof. 

 Joseph Leidy, telling him I believed the " wolf-teeth" 

 were the remnants of the teeth that "ceased to be 

 functionally developed," and asked his opinion about 

 the matter. Writing under date of "Philadelphia, 

 Nov. 26, 1878," he said : 



* * * "I think you are right in supposing that 

 the little premolars referred to by Prof. Marsh as the 

 ' corresponding upper teeth,' which ' ceased to be func- 

 tionally developed,' are the so-called f wolf-teeth.'" 



Another letter, addressed to Prof. Theodore Gill, 

 elicited the following reply, which was dated "Smith- 

 sonian Institution, Washington, D. 0., Nov. 25, 1878:" 



* * * " The complete dentition of the adult 

 horse is represented by the formula: I., f ; 0., j; 

 D., ; P. M., |; M., | x 2=42. The < small wolf or 



