22 



THE MAMMALIA. 



The Worm-tonguf.d Edentates {VermiJingiiia). Dis- 

 tinguished by the possession of long worm-like 

 tongues, always coated with an adhesive saliva, 

 which enables them to be used as organs of pre- 

 hension. 



The Ant-eaters. 



The Pancwlins. 



the marsupials or pouch-bearing 



MAMMALS {Marsupiitlia). 



Non-placental mammals with free digits bearing nails 

 or claws. The young are bom in a very imperfect 

 condition, and complete their development attached 

 to teats situated in an external abdominal pouch 

 (niarsupium) supported by two special bones (mar- 

 supial bones) attached to the pelvis. The dentition 

 is usually complete but permanent, except in the 

 case of a single premolar, which is shed and 

 renewed. The lower angle of the lower jaw behind 

 is turned inwards. 



The Opossums {Dide/p/iyida). With five digits on 

 all four feet, and with a very long and strong 

 hallux, which is completely opposable as in 

 monkeys. 

 The Predaceous Marsupials {Rapacia). 



The Perameles Family {Peramelida). Longeared 

 marsupials with tubercles on the molar teeth, 

 adapting them for crushing insects, the first digit 

 of the fore-feet represented only by a wart or 



tubercle, that of the hind-feet entirely absent, 

 while the second and third digits in the hind- 

 feet are very thin and united together down to 

 the claws. 

 The Dasvure Family {Dasyurida). With a more 

 or less well-marked carnivorous dentition. 



The Fruit-eating Marsupials {Carpophaga). 



The Phalanger Family {Phalangistidd). With the 

 second and third digits of the hind-feet united, 

 a nailless opposable hallux, and well-developed 

 marsupial pouch. 



The Herbivorous Marsupials {Poephaga). Com- 

 posed of forms well adapted for leaping; always 

 with five digits, armed with strong claws on the 

 short fore-limbs, and very long hind-limbs fitted 

 to bear the whole weight of the body. 



The Root-eating Marsupials {Phizophaga). Com- 

 posed only of a single genus, the wombats 

 {P/iascolomys), with a dentition exactly like that of 

 a rodent. 



THE MONOTREMES {Monotremata). 



Non-placental mammals without true teeth, with the 

 genital and urinary ducts opening along with the 

 rectum into a common chamber (cloaca). They 

 have neither marsupial pouch nor teats, but have 

 milk-glands and marsupial bones. 



The Ornithorhynchus. 

 The Echidna. 



: : :: •: NOTE 



ON POINTS CONNECTED WITH GEOLOGY REFERRED TO IN THIS WORK. 



In the following pages a section under each 

 order of the Mammals is devoted to the question 

 of the presumed origin or descent of the group, 

 which involves the consideration of its distribution 

 in time. With the view of assisting the reader 

 in following the reasonings in the sections alluded 

 to, a geological table showing the sequence of 

 the rocks forming the crust of the earth is here 

 added. Where subordinate members of the systepis 

 given in this table are mentioned in the text, such 

 sub-divisions, for example, as the Keuper or New 

 Red Marl, or local formations, like the Stonesfield 

 Slates, or the Purbeck Beds, an indication is always 

 given of the system to which they belong, so that 



a reference to this table will enable the reader to 

 understand in a general way the relative order in 

 time of the extinct forms spoken of. 



It may here be mentioned, however, that the 

 order of the strata, as shown in this table, must 

 not be understood as giving any indication of the 

 length of time separating forms belonging to differ- 

 ent systems. The thickness of the rocks composing 

 these systems varies greatly, and there is presum- 

 ably a corresponding variation in the length of 

 time that has elapsed during their formation. Thus, 

 though the first Mammalian remains are found in 

 the Tria.s, it may be inferred from the thickness of 

 the British strata, that the interval between their 



