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 There is, furthermore, a distinct tendency towards a disappearance of functional milk teeth, which is best seen in Sorex, where there are only seven milk teeth, none of which ever cut the gum. This suppression of the milk dentition is like that of the Marsupials, Edentates, and Whales, all of which appear to be—the first certainly are—ancient forms of mammalian life.

There is also a fairly well-defined, though shallow, cloaca in many genera. Finally, the testes are purely abdominal in some, and in none is there a full descent into a scrotum, as in the more highly-developed Eutheria.

'''Fam. 1. Erinaceidae.'—This family contains the genera Erinaceus, Hylomys, and Gymnura''.

Hylomys, considered by Dobson to fall within Gymnura, is kept separate by Leche. H. suillus is a Malayan animal, small in size, about 5 inches long, with a short tail. Like Gymnura it is spineless. The ears are decidedly large and nude. There is one pair of inguinal and one pair of thoracic teats. The colour above is a rusty brown with yellowish-white under parts. The palms and soles are quite naked. In its general form it recalls Tupaia very much more than its own immediate relatives. There is no doubt, however, of its systematic position when the skeleton and teeth are examined. A variety has been described from altitudes of 3000 to 8000 feet on Mount Kina Balu in Borneo. It has the complete dentition of forty-four teeth. There are fourteen pairs of ribs. As in Gymnura the tibia and fibula are united below. The genus is considered by Leche to be the oldest existing type of Erinaceidae.

Gymnura is also a Malayan form with the complete dentition of the last, but with fifteen pairs of ribs and a longer tail, consisting of twenty-three vertebrae as against fourteen. There is, as with Hylomys, but one species, G. rafflesii. This animal has a peculiar odour, resembling decomposed cooked vegetables.