402 MR. G. E. DOBSON ON THE HALLUX OF MAMMALS. [June 3, 



EXPLANATION OF THE PLATES. 

 Plate XXXIV. 



Fig. 1. Female hybrid bovine, B. Bom May 21, 1881. 



2. Female hybrid bovine, 0. Born March 12, 1S84 ; one month old. 

 (Drawn April 14, 1884.) 



Plate XXXV. 



Fig. 1. Female hybrid bovine, C. Born March 12, 1884; eleven weeks old 

 (Drawn June 1, 18S4.) 



3. On the. Unimportance of the Presence or Absence of the 

 Hallux as a Generic Character in Mammalogy, as shown 

 by the gradual Disappearance of this Digit within the 

 limits of a single Genus. By G. E. Dobson, M.A., 

 F.R.S. 



[Received May 29, 1884.] 



The presence or absence of the hallux has been so often considered 

 by mammalogists as sufficient ground for the formation of a new 

 genus, that any instances in which it can be shown that this digit 

 may disappear within the limits of a single genus, the species of 

 which are united by indissoluble bonds of common affinity, is of 

 much interest and importance. 



Of all the genera of Placental Mammals few exhibit such close 

 affinities among the species composing them as Erinaceus, which may 

 be taken as an example of a thoroughly natural genus incapable of 

 division into subgenera or well-marked subdivisions of any kind. 

 Nevertheless this genus has been divided, one species, E. albiventris, 

 having formed the type not only of a new subgenus (Atelerix, Pomel), 

 but even of a new genus (Peroeckinus, Fitzinger). 



Although, as already pointed out in my ' Monograph of the 

 Insectivora' 1 , I have long considered the absence of the hallux in 

 E. albiventris of little importance, seeing that that digit presents all 

 degrees of development in the other species, from its comparatively 

 large size in E. europceus clown to its rudimentary condition in E. 

 diadematus, where it is only 4 mm. in length, yet, up to the time of 

 writing this note, I was unable to find any examples in which the 

 extent of development of this digit might be said to be truly inter- 

 mediate between its condition in E. diadematus and E. albiventris. 

 Lately, however, in a collection kindly made for me at Lagos by the 

 Colonial Surgeon, Dr. J. W. Rowland, 1 found specimens of E. albi- 

 ventris (well preserved in alcohol), which furnish all the material 

 required. 



The specimens referred to consist of examples of an adult female, 

 in which the second upper premolars of both sides have already been 



1 ' A Monograph of the Insectivora, Systematic and Anatomical,' pt. i. p. 11 



