Article VII.— A FOSSIL HEDGEHOG FROM THE 

 AMERICAN OLIGOCENE. 



By W. D. Matthew. 



The Hedgehog family (Erinaceidse) has hitherto been found 

 only in the Old World (Europe, Asia, and Africa). It includes 

 three living and five extinct genera, ranging from Lower Oli- 

 gocene to recent. It has been divided into two subfamilies, 

 one including the modern hedgehogs (Erinaccus) and one ex- 

 tinct genus {Palceoerinaceus), the other with two modern 

 genera, Gymnnra and Hylomys, — small rat-like East Indian 

 insectivores, — and four extinct genera, Necrogymnuriis, Ga- 

 lerix, Lanthanotheriiim, and Tetracus. The subfamilies are 

 distinguished as follows: 



ErhiaceincB. — Dentition -^^ . Palate imperfectly ossified. 



2.1.2.3 



Pelvis wide. Fur with spines. 



3.1.4.3 



Gymniirince. — Dentition . Palate completely ossified. 



3-I-4-3 

 Pelvis very narrow. Fur without spines. 



A related but more primitive family, the Leptictidee, is 

 found in the American Eocene and Oligocene. The dentition 

 is unreduced (except that there are only two upper incisors), 

 the molars subtriangular and extended transversely, while in 

 Erinaceidse they are subqttadrate and not extended trans- 

 versely. The Leptictidse might, however, without serious 

 straining of relationships, be included as a primitive sub- 

 family of Erinaceidae, with which they agree well enough in 

 skeleton and in most skull characters. There are four de- 

 scribed genera, Palceictops from the Middle Eocene, Leptictis, 

 Ictops, and Mesodcctcs, from the Lower Oligocene of the 

 Western United States. 



A true Hedgehog, of the Erinaceine subfamily, is repre- 

 sented by the front half of a skull from the Upper Oreodon 

 Beds of South Dakota, found by Dr. F. B. Loomis of the 

 American Museum Expedition of 1902. The dentition is that 

 of Erinaceus, but the teeth are less specialized, and in several 



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