NATURAL HISTORY MISCELLANY. 717 
mens derived from the Purbeck beds have been at last fully and 
entirely described by Professor Owen. Sir Charles Lyell elo- 
quently and suggestively pointed out, with reference to the im- 
portance of the Purbeck discoveries, “when the geologist inquires 
if any land animals of a higher grade than reptiles lived through 
any one of these three periods, the rocks are all silent, save one 
thin layer a few inches in thickness. This single page of the 
earth’s history has suddenly revealed to us in a few weeks the 
memorials of so many species of fossil mammalia that they al- 
ready outnumber those of many a subdivision of the tertiary se- 
ries and far surpass those of all the other secondary rocks put to- 
gether !” 
In this locality Mr. Beckles worked for many years at his own 
expense ; and the result was the discovery of an extensive series 
of fossils, which were placed in the hands of Professor Owen for 
description. Some of these in the meanwhile were described by 
other paleontologists; and a controversy was carried on, both in 
the “Quarterly Journal of the Geological Society” and in some 
ephemeral publications, as to the nature and value of the principal 
genus of mammalia that was discovered in the Purbeck “ dirt bed.” 
This species, Plagiaulax, contained in itself one of those text- 
examples on which the truth and verity of all our physiological 
deductions may rest. And it is rather with a view of offering our 
readers some notion of the intellectual canons on which a scien- 
tific man may determine the affinities of a species than of describ- 
ing the form itself, that we briefly call attention to what, perhaps, 
is one of the most interesting genera which modern science has 
unveiled to us. 
The jaw of a very minute animal presented, as was thought by 
Dr. Falconer, its original describer, some points of analogy with 
the characters exhibited by the jaw of the kangaroo-rat ( Hypsi- 
prymnus), and much controversy was expended at the time of its 
discovery and shortly afterwards, as to tke precise value of those 
features which led one eminent scientific man (alas! since de- 
ceased) to affirm from the form of the jaw and shape of one of 
the teeth that it was an herbivorous animal ; while Professor Owen, 
on the other hand, declared it to be a carnivorous marsupial. That 
two such eminent men could in this way differ on the most simple, 
the most elementary, and the most obvious fact in the science, 
naturally leads students to suspect either that the infallible can- 
