156 MUSTELID^:. 



AECTOIDEA. 

 Family MUSTELID^E. 



The first family in the third of the great groups into which the 

 typical Carnivora have been divided contains the martens and 

 weasels, the badgers and the otters, an assemblage of animals 

 varying more in external conformation, and also in the characters 

 of the teeth, than is the case in any other family of Carnivora. All 

 agree in the possession of a single upper true molar on each side, 

 and all have two lower molars in each ramus of the mandible ex- 

 cept Mellivora, which has but one. The number of premolars is 

 variable, and even that of the incisors is not constant. There is no 

 alisphenoid canal. Several genera possess the power of diffusing 

 at will from their anal glands an excessively foetid fluid. Five 

 toes occur on all feet. 



The Mustelidce are somewhat difficult of arrangement when all 

 the genera are taken into consideration ; but the Indian forms fall 

 easily and naturally into the three subfamilies amongst which the 

 types belonging to the family have been distributed. These sub- 

 families are readily distinguished by the characters of the feet and 

 claws. 



A. Toes short, partially webbed ; claws short, com- 



pressed, acute, curved, often semirectractile. 

 Upper posterior molar of moderate size, elongate 

 transversely. Terrestrial and arboreal Mustelince. 



B. Foot elongated ; toes straight ; claws non-retrac- 



tile, slightly curved, non-com pressed, blunt, those 

 of the fore feet especially large. Upper posterior 

 molar variable. Habits mostly terrestrial and 

 fossorial Melince. 



C. Feet short, rounded ; toes webbed ; claws small, 



curved, blunt. Head broad and much depressed. 

 Upper posterior molar large and quadrate. 

 Habits aquatic Lutrince. 



The above arrangement is identical with Blyth's in his 'Catalogue 

 of the Mammalia in the Museum of the Asiatic Society,' but Jerdon 

 classed the badgers and their allies in a distinct family apart from 

 the weasels and otters. 



Throughout the Mustelidce the form of the skull changes with 

 age, even more than in other Carnivora. The breadth across the 

 zygomatic arches increases, whilst the width of the skull between 

 the orbits diminishes to an extraordinary degree. The sagittal and 

 occipital crests increase long after the animal is fully adult. There 

 is also in many forms a great sexual difference in size. A remark- 

 able example is described by Mr. Thomas (P. Z. S. 1886, p. 125). 



