MAMMALIA. 81 



jaw of a young Triconodon from the Purbeck Beds of Swanage Table-case 

 is believed to show a single tooth being replaced in the 14a - 

 typical marsupial fashion (see p. 1 7). The unique collection 

 from the Purbeck Beds, made by Mr. S. H. Beckles, is 

 arranged in Table-case 14b, and comprises several jaws of 

 Triconodon (Fig. 74) and Spalacotheriwm (Fig. 75), besides 

 remains of other genera described by Owen in his " Mono- 

 graph of Mesozoic Mammals " (Palseont. Soc, 1871). With 

 these are some jaws from the Stonesfield Slate, including the 

 original specimen of Phascolotherium bucklandi (Fig. 76), 



Fig. 76. — Lower jaw and teeth of Phascolotherium bucklandi, from the 

 Stonesfield Slate of Oxfordshire ; outline-fig. nat. size. (Table-ease 14a.) 



which was so much discussed by Cuvier, Agassiz, and others 

 early in the last century. Drawings of the American 

 Mesozoic jaws are placed with this collection for reference 

 (Fig. 77). 



Sub-class III. — Peototheeia. 



Oedee XL— MULTITUBERCULATA. 



In some of the jaws of Mesozoic mammals, and in a 

 few similar specimens from the base of the Eocene, both in 

 Europe and North America, there are crushing teeth which 

 bear two or three rows of tubercles or are provided with 

 tubercles round the edge. The otherwise unknown animals 

 to which these jaws belong are named Multituberculata, and 

 they are supposed to be related to the ancestors of the 

 living egg-laying mammals (Monotremata) of the Australian 

 region, because the young Ornithorhynchus has somewhat 

 similar multituberculate teeth (see Fig. 82, p. 85). 



G 



