TORTOISES AND TURTLES. 



393 



Fig. S, MATAMATA (.Chelys fimbriata). 



shields of the carapace, which is serrated on its margins, In length the 

 shell of the matamata reaches fifteen inches. In habits this tortoise is a 

 fresh- water and chiefly carnivorous animal ; and it is probable that the 

 tufts on the neck are for the purpose of attracting its prey within easy reach 

 of its jaws. In addition to its 

 other characteristics, the matamata 

 has a proboscis to the snout, but 

 this is wanting in the other South 

 American long-necked members of 

 the family, which form the genus 

 Hydromedusa. These tortoises also 

 differ in the comparative smooth- 

 ness of the shell, and in having 

 only four claws to each foot. The 

 remaining three South American 

 genera, namely Hydraspis, lihinemys, and Platemys, have the neck propor- 

 tionately shorter. Three generic types of the family are met with in 

 Australia and Papua, one of which (Ckelodina) has the neck very long, while 

 in the other two (Elseya and J^mydura) it is relatively shorter. 



The largest member of the whole sub-order is the great fresh- water tortoise 

 of the Amazons (Podocnemis expansa), whose shell often measures two-and-a- 

 half feet in length. Together with its allies, this species 

 belongs to the second family of the sub-order, characterised Family 



by the presence of a pair of mesoplastrals between the hyo- Pclomedusidce. 

 and hypoplastral bones, the total number of elements in the 

 lower shell thus being brought up to eleven. The neck can be fully with- 

 drawn into the shell, and the skull has a lateral bony arch. The genus 

 Podocnemis affords a remarkable example of discontinuous geographical dis- 

 tribution, six of the species being inhabitants of South America, whereas the 

 seventh is found in the distant island of Madagascar. In this genus the 

 hinder part of the skull is completely roofed over by bone ; but this is not 



the case in the other two genera 

 of the family. Of these, Pelo- 

 medusa, which has only a single 

 species, inhabiting both Madagas- 

 car and Africa, resembles Podo- 

 cnemis in that the two mesoplas- 

 tral bones only show themselves on 

 the sides of the lower shell, and 

 are thus widely separate in the 

 middle line. On the other hand, 

 in Sternotkcerus the same two 

 bones are as fully developed as 

 the other elements of the plastron, 

 in the median line of which they 

 come into contact with one another. 

 The whole of the species of this 

 genus are African, but one ex- 

 tends its range into Madagascar. 

 The great Amazonian species of Podocnemis is of considerable value to the 

 natives of some parts of tropical America, on account of its eggs, which are 

 collected in vast quantities, mainly for the sake of the oil they yield. 



Fig. 9. AMAZONIAN FRESH-WATER TOB.TOISE 

 (Podocnemis expansa), 



