320 Reviews — Prof. S. F. Qsborn — Molars of Perissodactyla. 



duced three convenient new descriptive terms, which will be equally 

 applicable to the molars of other Perissiodactyles. It appears that 

 the outer wall of the Ehinoceros molar is formed by the union of 

 the primitive paracone {pa.) with the metacone (me.), to which is 

 added the anterior ridge (a.) ; and for this outer wall the term 

 ectoloph is suggested. The anterior transverse crest, formed by the 

 union of the paracone (pa.), protoconule (pi.), and protocone (pr.) 

 is termed the protoloph ; while for the posterior transverse crest, 

 compounded of the metacone (me.), metaconule, and hypocone (hy.) 

 we have the name metaloph. 



Fig. 5. — Left upper molar of Ehinoceros palceindicus. Letters as in Fig. 2. 

 a. to me. is the ectoloph ; a. to pr. the protoloph ; and me. to h^. the 

 metaloph. The process projecting from the metaloph into the median 

 Talley is the crotchet. 



In the primitive Ehinoceros molar the three elements — anterior 

 ridge, paracone, and metacone — of the ectoloph are represented by 

 distinct vertical ridges ; but some or all of these tend to disappear 

 with the increasing flatness of the outer surface of this part of the 

 tooth as specialization increases. And it is somewhat noteworthy 

 that while in the most specialized types of teeth, like those of the 

 Indian Rhinoceros, of the two African species, and of the extinct 

 Woolly Ehinoceros, the development of the paracone is less marked 

 than in the more generalized Sumatran and Javan species ; yet the 

 ridge marking the metacone is decidedly more pronounced. Although 

 there is no distinct representative in the Ehinoceros molar of the 



