264 THE DENTAL SYSTEM OF THE PRIMATES [SECT. A 



Hominidae with a moderate degree of frequency, and there is one 

 record for Cynocephalus (De Terra, op. cit, p. 269), but in no 

 other of the Primates above the Lemurs so far as I am aware. 

 As for the Lemuroidea, it is stated by De Terra (op. cit, p. 241) 

 that Professor Leche has recognized double-rooted canine teeth in 

 the deciduous as well as the permanent dentition of those animals. 

 At least three important points arise for consideration here. 



(a) The mammals in which the double-rooted canine has 

 been observed are : 



(1) Hominidae (as an anomaly). 



(2) Lemuroidea (? anomalous). 



(3) Certain Insectivora, ex. gr. Microgale 1 ; also Galeo- 



pithecus (normal). 



(4) Certain of the earliest fossil mammals, viz. Diplo- 



cynodon, of the Upper Jurassic (normal). 



Thus it might seem that the double-rooted type of canine 

 tooth is the original one. Yet Professor Gregory in admitting 

 this possibility, gives a word of warning to the effect that the 

 single-rooted canine is found in the same groups of animals and 

 throughout just as great a range of geological time, as the more 

 complex form. 



(b) The occurrence of double-rooted canine teeth supports the 

 view (attributed to Sir Ray Lankester by Professor Osborn, 

 Evolution of Mammalian Molar Teeth, 1907, p. 194), that the canine 

 tooth is really a modified premolar tooth. 



(c) Among the Hominidae, canine teeth with double roots 

 are peculiarly frequent in early British crania as contrasted with 

 all others. This was noticed b} r Rolleston many years ago. The 

 observation is confirmed by specimens in the Cambridge Collection, 

 which includes a remarkable mandible (of mediaeval age) in which 

 the right canine tooth has two roots, while the first premolar 

 tooth (adjoining it) has but the normal single root. 



The other anomaly of the canine teeth consists in the occa- 



1 Gregory, Bulletin of the American Museum of Natural History, Vol. xxvu. 

 1910, pp. 289, 290. 



