46 ERINACEID^— ERINACEUS 



described as indicating a "True Hedgehog" of ancestral type, 

 apparently intermediate in form between Erinaceus and Gym- 

 nura of the old world. These were also thought by Trouessart 

 to be connected by his Neotetragus sinensis from western China 

 {Ann. and Mag. Nat. Hist., October 1909, 389-391), but 

 Thomas has since shown (Proc. Zool. Soc, London, 191 1, 162, 

 published March 191 1) that the true affinities of this form are 

 with the gymnurine Hylomys, without any special leaning 

 towards the Erinaceinse. 



Hedgehogs are of considerable antiquity, and date at least 

 from the upper and middle Miocene of European strata. The 

 ancient Egyptians have left drawings of a member of the closely 

 allied Hemiechinus auritus {Nature, 30th June 1904, 208; 

 see also Keller, p. 20, fig. 7). 



Generic characters: — The true hedgehogs are short-tailed 

 insectivora with rudimentary caudal vertebrae, imperfectly ossified 

 palate, and wide pelvis. 



The upper surface and sides of the body, but not of the tail 

 and head, are covered with spines, and, by the help of a special 

 development of muscles, the skin of the back can be drawn 

 downwards and forwards over the head and limbs. The 

 animal tucks in its head into the interior of the "ball" thus 

 formed, and is protected on all sides from ordinary attacks. 



The spines are longitudinally grooved, the intervening ridges 

 being smooth. 



The hair is harsh. 



The ears are very short, always less than half the length of 

 the head (Plate V., Fig. 3). 



There are six to ten paired mammae. 



In the skull the pterygoid fossae are well developed, with 

 the processes not hollow and taking no part in the osseous 

 bullae ; the postglenoid process is much smaller than the post- 

 mastoid, and its interior is solid, not hollow. 



There are thirty-six teeth (Fig. 22, p. 54) arranged as — 



- — -, c , pm^ — ?, m^ — ^ = ii(,. 



2-2 i-i-^ 2-2' 3-3 ^ 



The canines and anterior premolars are usually described as 

 single-rooted, but vary very much in this respect. 



