THE BRITISH MAMMALS I ORDERS, FAMILIES, ETC. IQ 



In the upper jaw the molars are reduced to one ; in the lower there 

 are frequently two. There are distinct condyloid and glenoid 

 foramina. The genera appearing on our list 'are Lutra, Meles, 

 Mustda, and Putorius (Plates V., VI., VII., 23 to 29). 



In the Phocidas the feet are modified into flippers, on each of 

 which there are five digits ; the hinder pair are joined to the tail by 

 the interdigital membrane. The eyes are large, exposed, and flat. 

 There are no outer ears. The upper incisors are pointed and vary 

 in number; the canines are large; there are four premolars and one 

 molar, and these are flat and pointed, not broad and tuberculated ; 

 there are no flesh teeth. The frontal is without apostorbital process. 

 There are no clavicles. Our list includes three genera of this family, 

 Cystophora, Halichcenis^ and Phoca (Plates VIII. and IX., 30 to 34). 



The Rodentia are distinguished by their long incisors, which have 

 chisel edges owing to the enamel being mainly or entirely on the 

 front surface. These teeth have persistent pulps instead of roots, 

 and consequently grow continuously. The upper incisors are two 

 or four in number, generally two ; the lower are never more than 

 two. There are no canines. The premolars are always less than 

 three, and. in some cases, are wanting. They are separated from 

 the canines by a diastema, the gap being lined by the hairy skin of 

 the face. When present, they are similar to the molars in having 

 tubercnlated or laminated crowns. The premaxillaries, containing 

 the basal portions of the upper incisors, are large, and separate the 

 nasals from the maxillaries ; the orbits are not surrounded with 

 bone, and, as a rule, there is no postorbital process. A zygomatic 

 arch is always present. The condyle of the mandible is longitudinal, 

 so that the lower jaw works backwards and forwards. There are 

 twenty-two families, of which four, the Sciuridae, Myoxidae, Muridae, 

 and Leporidae, are represented in these islands. 



In the Sciuridte there are two upper incisors. The angular por- 

 tion of the mandible rises sharply from the lower edge of the bony 

 socket of the incisor ; the zygomatic arch is slender ; the frontal is 

 broad ; the postorbital process is long ; the infraorbital opening is 

 small, the palate broad. There are two premolars in the upper jaw 

 and but one in the lower, the outer premolar being small and some- 

 times deciduous ; the molars are rooted and tubercular. The fibula 

 is distinct ; the tail is cylindrical and bushy ; the eyes and earj are 

 large. The Squirrel is the only British representative (Plate X., 35). 



In the Myoxidae there are two upper incisors. The mandible has 

 a slender coronoid process ; the zygomatic arch is slender ; the 

 frontal is narrow ; there is no postorbital process ; the infraorbital 

 opening is narrow and high. There is only one premolar in the 

 upper jaw, as in the lower ; the molars have roots and transverse 

 folds of enamel. The tibia and fibula are united. The only British 

 representative is the Dormouse (Plate X., 36). 



In the Muridae there are two upper incisors. The zygomatic arch 

 is slender, the jugal is a mere splint ; the frontal is contracted, there 

 is no postorbital process ; the infraorbital opening is high, wide 

 above, and narrow below. There are no premolars. The tibia and 

 fibula are united. The British genera are Microtus and Mus (Plates 

 XI., XI I., XI II., 37 to 45), 



