133 



by the oblique chisel-like cutting surface of the more perfect incisor : 

 and it is not without interest to find that the presence of ' dentes scal- 

 prarii ' at the anterior part of the mouth has not been necessarily limited 

 to Mammalia of small size. 



565. A left lower incisive tooth of the Toxodon platensis . 

 From the cliffs at Bahia Blanca. 



Presented by Charles Darivin, .Esq., F.R.S. 



Family Proboscidia. 



Genus Elephas. 



The following series of the molar teeth of the fossil Elephant or Mammoth is 

 subdivided so as to illustrate first, their form, — second, their structure, — third, 

 their groivth, — and fourth, their varieties. 



Form. 



566. An upper molar tooth of the right side, of a full-grown and probably aged 

 Mammoth {Elephas primigenius , Blum.). 



It presents an equilateral triangular figure, the narrow base being 

 formed by the grinding or exposed surface of the tooth ; and it consists, 

 as in the existing Elephants, of a crown and fangs, the crown deeply 

 cleft by transverse parallel fissures into a series of broad and thin plates, 

 which, being developed from their summits towards the common uniting 

 base, continue separate, or joined together only by the adhesion of their 

 outer covering of cement, until the base of the crown and the fangs 

 begin to be formed. As each lamellar division of the crown is covered 

 by a layer of enamel and then by a layer of cement, they represent, while 

 ununited, distinct teeth, and are then termed ' denticules.' Each plate is 

 also subdivided by vertical fissures extending from the apical margin to 

 unequal depths, and as calcification commences at the apices of these sub- 

 divisions, so each plate or denticule consists at the beginning of a series 



