350 PALAEONTOLOGY. 



law in the interpretation of fossil remains as defined by the 

 illustrious founder of paleontology. 



Genus Spalacotherium, Ow. — The next stratum overlying 

 the older oolites in which mammalian remains have been 

 detected, is a member of the newest oolitic series at Pur beck, 

 Dorsetshire, called the " marly" or "dirt-bed;" they have 

 been described under the name of Spalacotherium* tricuspidens. 

 The specimen here selected (fig. 117) to exemplify the species 



is a right ramus of the lower 

 jaw. The posterior half con- 

 tains four teeth, and, instead 

 Fig. 117™" °f shewing the compound 



Spalacotherium tricuspidens (twice uat. Structure which that part of 

 size), Purbeck beds. ,-i i •-, -, • x1 -■■ -, 



h the jaw exhibits m the lizard 



tribe, it is undivided. The crowns of the teeth are long, nar- 

 row, and tricuspid, the inner part of the crown being produced 

 into a point both before and behind the longer cusp wdrich forms 

 the chief outer division of the crown. Each of these teeth is 

 implanted by a fang divided externally into two roots, in a 

 distinct socket in the substance of the jaw. The multicuspid 

 crown, the divided root of the tooth, its complex implantation, 

 and the undivided or simple structure of the ramus of the 

 jaw, all concurred, therefore, to prove the mammalian nature 

 of this fossil. Other specimens shewed that the Spalaco- 

 therium had ten molar teeth in each ramus of the lower jaw, 

 preceded by a small canine and incisors. The anterior molars 

 are compressed, increase in height and thickness to the sixth, 

 and from the seventh decrease in size to the hindmost, 

 which seems to be the last of the series. The sharp multi- 

 cuspid character of so much of the dental series as is here 

 preserved, repeats the general condition of the molar teeth of 

 the small insectivorous Mammalia in a striking degree : one 

 sees the same perfect adaptation for piercing and crushing the 



* From <rnu\u.%, } a mole : tvpiov, a beast. 



