80 MIOCENE FAUNA. 



genus for them. The fossil family of chinchillas includes the genus 

 Issiodoromys, of which one species (/. pseudoncema, Croiz.) has 

 been discovered at Aarwangen, and the genus Theridomys, one 

 species of which (T. Blainvillei, Gerv.) comes from the same 

 locality and a second from Roehette. The Theridomys have 

 smooth incisors, and the molars of the lower jaw have a fold on 

 each side which divides them into two lobes. 



The beaver-like rodents (Castoridse) are represented in Swit- 

 zerland by two species of Chalicomys, a genus which is distin- 

 guished from the Castor by the form of the roots of the teeth 

 and the folding of their enamel. The larger species (C. Jageri, 

 Kaup) must have been very like the common beaver. It was, 

 however, a little smaller (about i\r to |), and had narrower 

 molars. This is the commonest mammal of Kapfnach near 

 Horgen ; so that numerous families of it must have lived in the 

 Miocene peat-mosses of that district. The second species (C. 

 minutus, Meyer), which is scarcely distinct from C.Eseri, Meyer, 

 is only about half the size of the living beaver. It is much less 

 common than the preceding species, but is not confined to the 

 Upper Miocene, making its appearance in the lignites of the 

 Hohe-Rhonen and Rochette. As it also occurs in the lignites 

 of Elgg, it probably inhabited Switzerland during the whole 

 period of the Miocene. 



Only six species of carnivorous Mammals have been found in 

 the Swiss Miocene, among which there are some which represent 

 the hysenas, otters, and civets. The largest and most remark- 

 able animal of this order (Hycencelurus Sulzeri } Bied.) was dis- 

 covered by Dr. Biedermann in the Miocene of Veltheim. 

 Judging from the size of the jaw and teeth, it was considerably 

 larger than the Bengal tiger, and was characterized especially by 

 the wide gap between the great canine tooth and the first molar. 

 In the dentition of the lower jaw it agrees with the tiger, but in 

 that of the upper jaw rather with the hyaena*. 



* In the Carnivora one molar tooth is furnished with a sharp cutting-edge, 

 and is usually larger than the rest ; it is known as the (( flesh-tooth." The 

 teeth in front of this are the premolars or false molars, whilst the posterior 

 teeth are called tubercular molars. Hycencdwrus has, in the upper jaw, five 

 molars, like the hysenas, and in the lower jaw only three, like the tiger (the 

 hysenas having four). 



