530 M. A. C. Hinton — British Fossil Shrews. 



Neomys has gone a little further, and, in adopting an aquatic 

 habitat, in a different direction, which has to some extent influenced 

 its external characters. A premolar has been lost above; the large 

 lower incisor has been simplified — only one of the primitive denticles, 

 in addition to that forming the point of the tooth, persisting ; and 

 the peculiar modification of the mandibular condyle, and the glenoid 

 cup into which it fits, has proceeded further. 



The mandible offers good characters for the determination of the 

 fossil species, and of the earlier British forms little more is known. 

 The strange features presented by the articulation of the lower 

 jaw with the skull in the Shrews were first described by Cuvier, 1 

 and more fully by Winge 2 and Parker. 3 The mandibular condyle 

 bears two facettes, an upper and a lower, widely separated by 

 a non-articular tract of bone, and, which correspond with two facettes 

 upon the squamosal. In Sorex (Figs. la-\Aa) the middle non-articular 

 region is as broad as, or broader than, the superior facette, and the 

 lower facette is not prolonged lingually. In Neomys the non-articular 

 region is much narrowed, so that it appears on the posterior view 

 of the condyle as a slender rod of bone connecting the two facettes, 

 the lower facette having in addition a great lingual prolongation 

 (Figs. la-Aa). In Sorex the foramen ovale passes forward between the 

 squamosal and alisphenoid, its mouth, wholly concealed by a process 

 i)f the squamosal, lying internally to and a little below the lower glenoid 

 facette. 4 In Neomys the lingual extension of the lower glenoid facette 

 prevents the foramen ovale from opening so far forwards ; it therefore 

 has its mouth behind the glenoid cup, and is completely visible on 

 the lower view of the skull. 5 



Sorex. 



Dental formula : i. \^-^ c. \ p. i±^ m. 1^| = 32. 6 Lower 

 incisor with three or four long persistent denticles. Middle non- 

 articular part of condyle not reduced in breadth, lower condylar 



1 Cuvier, Legons cPAnatomie Comparee, 2nd ed., t. ii, p. 323, 1837. 



2 Winge, Vidensk. Med. Nat. Foren. Kjobenhavn, 1877, pp. 119, 121, etc. 



3 Parker, " On the Structure and Development of the Mammalian Skull." — 

 Part III, Insectivora : Phil. Trans., pt ? i, pp. 213-15, pi. xxxi, figs. 3, 3a, 10, 

 cd.p., gl.c, 1885. 



4 Parker, op. cit., p. 217, pi. xxxi, figs. 2, 3. 



5 "Winge, op. cit., p. 134, fig. 6; Parker, op, cit., p. 217. 



6 Notwithstanding the fact observed by E. Brandt, viz. that the premaxilla 

 holds fou/r teeth, I prefer to follow Winge and regard the last of these teeth as 

 the canine, and not as inc. ■* — a tooth quite unknown among Placentalia. The 

 premaxilla has grown that it may accommodate the enlarged first incisor, and 

 in so doing it has embraced the vestigial canine. There is nothing more 

 remarkable in this than there is in the fact that the upper incisor of most 

 rodents bursts through the premaxilla behind and attains a seat in the maxilla. 

 The transgression in either case receives a physiological explanation (see Winge, 

 " Jordfundne og Nulevende Pungdyr fra Lagoa Santa," E Museo Lundi, 

 ii (11), p. 122, Anm. 39, 1893; Vidensk. Med. Nat. Form. Kjobenhavn, 1881, 

 pp. 12, 13, and 1882, p. 65). I also prefer to write the premolar formula in 

 Hensel's way (" Ueber Hipparion Mediterraneum," Abhand. konigl. Akad. 

 Wiss. Berlin, 1860, p. 78). From the excessive reduction of the tooth here 

 called p. - we may infer that the missing tooth in Sorex is p. -. 



