424 MK. E. T. NEWTON ON THE VERTEBRATE FAUNA [Aug. 1 899, 



from this the edges of the muscular attachments diverge, and, 

 passing forward, curve suddenly outward to end in the post-orbital 

 processes of the frontals, which are prominent and directed some- 

 what backward. The interorbital space is smooth and depressed. 

 The antorbital process of each frontal is broad, and is continued 

 outward by the maxilla : this, descending in front of and below 

 the orbit, forms the extremely broad plate which is a characteristic 

 feature of this skull. The jugal bone extends outward beyond the 

 maxilla, and passing backward joins the process of the squamosal, 

 the anterior extremity of the latter marking the greater width of 

 the skull. The premaxilla is comparatively short. 



The palate is almost perfect on the right side ; all the alveoli are 

 preserved, showing that the anterior cheek-tooth had one large fang, 

 while the other four teeth had each three fangs — a large inner one 

 (not so large as that of the front cheek-tooth), and two much 

 smaller outer fangs. The right premaxillary foramen is a slit 

 occupying the hinder half of the bone, and indenting the front of 

 the maxilla. There is a median spine at the hinder border of the 

 palatine bones. 



A comparison with the series of skulls in the Natural History 

 Museum at South Kensington shows that this Ightham Spermophilus 

 is nearly related to, if not identical with, the Siberian Sp. erythro- 

 genys. The lower jaw, as we have seen, agrees with that from the 

 Mendips, which Dr. Falconer also considered most closely related to 

 the same species, and called Sp. erythrogenoides. One peculiarity 

 of the Ightham skull is its great width, chiefly due to the wide- 

 spreading jugal arch ; and this feature, among skulls of corre- 

 sponding size, is most nearly represented by 8p. erythrogenys. 

 None of the skulls of Sp. altaicus {=Sp. Eversmanni) in the Natural 

 History Museum are so wide across the jugals, but they are wider 

 between the orbits. In other respects there is much resemblance 

 between the last-named species and the Ightham Spermopliilus. 

 The want of recent skeletons and the imperfections of the fossils 

 prevent a definite reference of this Spennophilus to >S/>. erythro- 

 genys ; and it will be best, therefore, to follow Dr. Falconer and to 

 include it with the Mendip specimens in his Sp. erythrogenoides . 

 I should also refer to the same species the Spermophil as-rema^ins 

 from the Brick-earth of Crayford and Erith. 



The skulls from the Fisherton Gravels, preserved in Dr. Black- 

 m ore's Museum at Salisbury, are much like that from Ightham, 

 and possibly may belong to the same species, for there is a 

 similar expansion of the jugal arch, and a like narrowness of the 

 interorbital region. However, points of difference are to be seen ; 

 and the lower jaw ^ has a more slender process for the articular 

 condyle. 



14. Mtjs Lewisi, Newton (=M. Abbotti, Newton). 



Since my previous paper was published, Mr. Barrett-Hamilton, 

 who has been working on the Mice of St. Kilda,^ called my attention 



^ See Falconer, ' Palseont. Mem.' vol. ii (1868) pi. xxxv, fig. 10. 

 > Proc. Zool. Soc. 1899, p. 77. 



