PURBECK FORMATIONS. 25 



The specimen, fig. 34, nat. size, and magnified twice nat. size at a, is the anterior half 

 and an impression of most of the remaining part of the left ramus of the lower jaw, its 

 inner sm-face exposed, showing the canine or canine-shaped premolar, c, and five following 

 teeth in place, a fragment of a sixth molar, and impressions of four succeeding molars. 

 The crown of the canine-shaped tooth is long, subcompressed, slightly recurved, pointed, 

 with a small post-basal tubercle. The adjoining tooth (i) has a compressed, pointed 

 crown, scarcely half the height of the canine and two thirds as broad at the base, with a 

 ridge along the inner side of the base, and a more developed posterior basal tubercle : it 

 is divided by a small interval from the canine. The second molar (2), with a shght increase 

 in size and a similar shape, has the fore part of the basal ridge developed into a low point, 

 and the hinder tubercle is relatively larger and more pointed. The third tooth (3) is 

 larger than either of the two preceding, but resembles them in form. The fourth (4), with 

 the same antero-posterior extent, has a lower crown, the middle cusp being relatively 

 shorter, but both the anterior and posterior ones are larger, and now begin to assume the 

 character of independent cusps ; their bases almost meeting upon the inner side of the base 

 of the middle cusp. The fifth molar, with a slight increase of size, shows a still further 

 development of the accessory cusps, which are slightly inclined backward, or project from 

 a more internal plane than the middle cusp. The impressions of the succeeding teeth show 

 that their middle cusp was longer in proportion to its basal breadth ; and thus agree, like 

 the foregoing teeth, with the teeth similarly marked in fig. 33. The canine-like tooth 

 seems to have a bifid fang ; the three succeeding premolars, implanted each by two fangs, 

 in this respect as in the general form and proportion resemble those of Ampldtlienum. 



The proportion of mandibular ramus here preserved and indicated is 1 inch 1 line, or 

 27 millimeters, in length, that of the Mole being 1 inch, or 25 millimeters. The crown of 

 the laniariform tooth is relatively longer, and the fourth tooth counting therefrom is of a 

 different form, being of much smaller size and of a more simple structure than is the corre- 

 sponding tooth, which forms the first true molar of the Mole. The greater number of molar 

 teeth indicated in the present and displayed in other specimens of the Spalacotherium 

 demonstrate its generic distinction from any known existing insectivore, placental or mar- 

 supial, the Myrmecobius having nine and the Chrysochlore having not more than eight 

 lower molars. The multident marsupial Myrmecobius is the sole existing Mammal, with 

 incisors and canines, that approaches the Spalacothere in the excessive number of the 

 molar teeth. Fig. 34b is a magnified view of the teeth marked 4 and 5 in fig. 34a, 

 showing the meeting of the accessory cusps on the inner side of the crown. 



The last two specimens afford grounds for determining the teeth in place in fig. 32 : 

 they are accordingly denoted by corresponding numerals. 



The evidence of the Mammalian nature of the above-described specimens, briefly 

 submitted to the Geological Society in 1854, excited an interest in further explorations of 

 their place of deposit. This was undertaken with characteristic ardour by Samuel H. 



4 



