174 GEOLOGY. 



" Only two specimens have been found, but evidently referable 

 to two distinct species, unequal in size and otherwise distin- 

 guishable. The largest P. Becklesit was about as big as the 

 English squirrel or the flying phalanger of Australia (Petaurus 

 Australis.J The smaller fossil P. minor, was probably only 

 1-1 2th of the bulk of the other. It is perhaps the more interest- 

 ing of the two, as Dr. Falconer has recognised in its two back 

 molars an unmistakeable resemblance to those of the Triassic 

 Microlesies antiquus, 



" The general resemblance of the jaws and teeth of the Pla- 

 giaulax to those of the living Kangaroo-rats raises a strong 

 presumption in favor of its having been both marsupial and 

 herbivorous. 



"On a review of all the fossils collected by Mr. Brodie and 

 Mr. Beckles, including the original Spalacotherium, together 

 with a lower jaw belonging to the Rev. P. B. Brodie, it appears 

 that we now possess the evidence of about fourteen species of 

 mammalia from the Middle Purbecks, to say nothing of numerous 

 remains of the highest osteological interest. They belong to 

 eight or nine genera, some insectivorous or predaceous, others 

 having affinities as yet doubtful, and one of a purely herbivorous 

 species, allied to the Kangaroo-rat of Australia. Some of the 

 predaceous species were marsupial, some of them probably 

 placental. 



"As all of them have been obtained from an area less than 500 

 square yards in extent, and from a single stratum not more than 

 a few inches thick, we may safely conclude that the whole lived 

 together in the same region, and in all likelihood they constituted 

 a mere fraction of the mammalia which inhabited the lands 

 drained by one river and its tributaries. They afford the first 

 positive proof as yet obtained of the co-existence of a varied 

 fauna of the highest class of vertebrata with that ample develop- 

 ment of reptile life which marks all the periods from the Trias 

 to the Lower Cretaceous inclusive, and with a gymnospermous 

 flora, or that state of the vegetable kingdom when cycads and 

 conifers predominated over all kinds of plants, except the ferns, 

 so far at least as our present imperfect knowledge of fossil botany 

 entitles us to speak." 



JOHN H, AUSTEN. 



