lo NATURAL SCIENCE. July. 



placed in Scmriis, from which they are distinguished by their dor- 

 mouse-like dentition. It will thus be seen how radical are the 

 changes in classification. 



Fossil teeth indicate that flying squirrels were abundant in the 

 Miocene ; and their occurrence there, with other circumstances, leads 

 the author to conclude that they have originated quite separately 

 from the Sciurinae, even if they belong to the same family. 



To enter into a discussion of the author's opposition to trituber- 

 culism would greatly exceed our limits ; but we may mention that he 

 believes that the Eutherian dentition has been derived from a direct 

 modification of the multituberculate type, and that tritubercuhsm is 

 a secondary feature due to reduction. Certainly, one of the figures 

 of a squirrel's molar reminds us very strongly of a molar of the duck- 

 bill, and, as far as it goes, is suggestive of the derivation of both 

 from a type in which the cusps were arranged in parallel longitudinal 

 series. To believe, however, that " Micvolestes may prove to be a 

 remote ancestor of the Eutheria," if it had incisor teeth at all Hke 

 those of its ally Plagiatdax, is, however, very difficult. We shall await 

 with interest what the Transatlantic palaeontologists have to say on 

 the subject. 



The Bison in the Caucasus. 

 Hitherto there has been much uncertainty as to the localities 

 where the bison still remains in a wild state in the Caucasus, and 

 naturalists are accordingly much indebted to Dr. Radde for clearing 

 up this point in a brief communication published in the Proceedings of 

 the Zoological Society (1893, PP- ^75-7)- The Doctor tells us that the 

 animal is confined to the district around the sources of the Laba and 

 Bjellaja on the north side of the range, extending eastwards from the 

 former locality to the springs of the Selentschuk. It is, however, 

 everywhere scarce, being generally met with only in twos and threes, 

 although occasionally as many as five have been seen together, and 

 once the tracks of a party of seven were detected. The survivors 

 appear to have lost their original settled habits, and to have become 

 wanderers in their last refuge, having, in some cases, crossed the 

 main ridge of the Caucasus and made their appearance on its southern 

 flanks. As there is, unfortunately, but too much reason to fear that 

 the Caucasian bison will, ere long, have ceased to exist, we are glad 

 to hear that Dr. Radde hopes to be able to publish an exhaustive 

 memoir on the anatomy, distribution, and habits of this animal. 



A Restoration of Ichthyosaurus. 

 Some months ago Mr. Lydekker referred in these pages (vol. i., 

 p. 514) to Dr. E. Fraas' discovery of a specimen of the extinct 

 marine reptile, Ichthyosaurus, showing the form and proportions of the 

 dorsal and caudal fins. In the second edition of the Rev. H. N. 

 Hutchinson's " Extinct Monsters," to the issue of which we referred 



