H54 



CHAPTER LXIII. 



CLASS MAMMALIA — continued. 



Orders Insectivora, Chiroptera, and Primates. 



Order IX. Insectivora. — The Insectivora are a group of small 

 Mammals, not very readily defined from the characters of their bones 

 and teeth. The teeth are well developed, and generally easily 

 separable into the usual four divisions, although in certain cases the 

 distinction between incisors, canines, and premolars is not very 

 clear. The dentition is diphyodont and heterodont; the cheek- 

 teeth are always rooted, and their crowns carry a number of minute 

 pointed cusps ; the crowns of the upper true molars being either 

 subquadrangular or triangular in shape. The first pair of incisors 

 in some cases are not in contact in the middle line ; and the canines 

 are often weak. The zygomatic arches of the skull are usually either 

 weak or entirely absent ; clavicles are present in all existing forms 

 except Potamogale ; in the carpus the scaphoid and lunar are 

 separate ; the feet are usually either entirely or partially planti- 

 grade, and their digits are generally five in number, with the ter- 

 minal phalangeals unguiculate, narrow, and subcylindrical. Certain 

 Insectivores, such as the Moles and Galeopithecus, are remarkable 

 as being the only Mammals in which ossified vertebral intercentra 

 are known to have been developed in the dorso-lumbar region. As 

 a rule the humerus has a foramen. 



Fossil forms apparently indicate a relationship on the one hand 

 with the Creodont Carnivora, and on the other with the Lemuroid 

 Primates ; those genera with square-crowned upper true molars ap- 

 proximating to the latter group, while those in which the crowns of 

 these teeth are triangular show the nearest affinity to the former. 

 Dr Schlosser concludes, with great probability, that the Lemuroids, 

 Insectivores, and Creodonts are all diverging branches from a 

 common stock, which may also have given origin to the Condy- 



