188 DR. C, J. rOESTTH MAJOR OX MIOCE]!fE SQUIRRELS. [Feb. 28, 



auhimiii), presents a closer approximation towards the hystricine 

 type in the relatiAely large infraorbital opening \ 



Again, another group of Ethiopian 8quii-rels (Sc. rufohrachiatus, 

 Sc. anmdaUis, Sc. punctatus, Sc. s7n>Yn.5is), belonging to the Sciunts- 

 inil(/aris-ty\ye by the characters of their dentition, show in the 

 conformation of their skull some approach towards Xerus ; whilst, 

 on tlie other hand, a few species, which from the fonn of their 

 skull cannot be separated from the Xcr^s-group, tend by the cha- 

 racters of their molars somewhat towards the Sciurus-vulr/aris- 

 type, as, for example, amongst Oriental Squirrels the Sc. iristriatus 

 and >SV, pahnarum. 



If we try to express by a systematic arrangement these vai'ious 

 relations, two courses appear open to us : either to unite Xerus 

 with Sec urns, or to create separate genera for those groups of 

 species which depart from Sciurns in approaching Xerits. However, 

 neither of these two suggestions seems satisfactory. By uniting 

 Xenis with Sciurns this last genus would, become still more 

 heterogeneous than it is already — Xems, sensu stricto, having 

 besides near relationships with Spermopjliilvs. By splitting up 

 Sciurus in various genera, the relationships of these last to Xerus 

 would not be seen in their true light. So that it appeared to me 

 more rational to adopt a middle course, viz., to detach from /S'cwn<,s 

 a certain number of species, which in their skull and dentition 

 show Xeroine affinities, and to unite them with Xerus, which last 

 genus would thus become composed of five subgenera (see the 

 table on the opposite page). 



The genus Sciurus, distinguished from Xerus by characters 

 of the skull as well as of the dentition, is dinded into three 

 subgenera, each of which is characterized by cranial and dental 

 peculiarities. 



Subgen. rt, £'oscm/'»s, contains the Oriental Giant Squirrels, which 

 by all authors on the subject, Anth the exception of Anderson, 

 have been recognized to be a distinct group ; in 1842 P. Grervais ^ 

 pointed out the characters of the skull. As I have already 

 stated more than once, the molars are perfectlj' brachj'dont, with 

 delicate rugosities of the enamel-covering. Only one superior 

 premolar. 



In the subgenus h. Sciurns we have four divisions : — (a) A small 

 group of Ethiopian Squirrels, characterized by the absence of the 

 minute superior premolar, and, as a compensation, a very elongate 

 posterior premolar. On the rest, the dentition is similar to that of 

 Sciurus I'ulgnris. I have before described the slight differences in 

 the molar pattern of division ft, containing the majority of so-called 



' Their skull in general, and most of all that of Sc. ebii, is so strikingly 

 Xeri<s-\ike, with the only exception of the jugalia not being depressed, that it 

 seems not possible to maintain them in the genus Sciurus if A'crvs be 

 maintained as such. 



- P. Gervais, " Description de I'Ecureuil Delessert, accompagn^e de quelques 

 remarques sur la famille des Rongeurs seiuriens," Magasin de Zoologie, 2. iv. 

 1842, p. 4. 



