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them show features that point more directly to Insectivores, and present evi- 
dences, based on specimens alone, would transfer them to the latter group, 
if they are to he retained in any modern order. This, however, has not yet 
been systematically attempted, and the known facts are against it. 
‘ In view of this uncertainty, it seems more in accordance with the present 
state of science to recognize the importance of the generalized characters of 
these early Mammals, as at least of ordinal value, rather than attempt to 
measure them by specialized features of modern types, with which they have 
little real affinity. With the exception of a very few aberrant forms, the 
known Mesozoic Mammals may be placed in a single order, which may 
appropriately be named Pantotheria. Some of the more important characters 
of this group would be as follows : — 
(1) Cerebral hemispheres smooth. 
(2) Teeth exceeding, or equalling, the normal number, 44. 
(8) Premolars and molars imperfectly differentiated. 
(4) Canine teeth with bifid or grooved fangs. 
(5) Rami of lower jaw unankylosed at symphysis. 
(6) Mylohyoid groove distinct on inside of lower jaw. 
(7) Angle of lower jaw without distinct inflection. 
(8) Condyle of lower jaw near or below horizon of teeth. 
(9) Condyle vertical or round, not transverse. 
1 The generalized numbers of this order were doubtless the forms from 
which the modern specialized Insectivores and Marsupials, at least, were 
derived. 
‘ Another order of Mesozoic Mammals is evidently represented by Plagi- 
aulax, the allied genus Ctenacodon * and possibly one or two other genera. 
These are all highly specialized aberrant forms, which apparently have left 
no descendants. This order, which may be termed Allotheria, can be distin- 
guished from the previous group by the following characters : — 
(1) Teeth much below the normal number. 
(2) Canine teeth wanting. 
(3) Premolar and molar teeth specialized. 
(4) Angle of lower jaw distinctly inflected. 
(5) Mylohyoid groove wanting. 
( These characters alone do not indeed separate the Plagiaulacidse from 
some of the Marsupials, and future discoveries may prove them to belong in 
that group, where they would then represent a well-marked sub-order.’ 
MINERALOGY. 
Crystallized Danburite . — In the American Journal of Science for August, 
1880, there is a paper by Professors Brush and Dana on the occurrence of 
this mineral at Russell, St. Lawrence County, New York. They received 
a number of specimens from a mineral collector in Northern New York, and 
amongst them were some prismatic white weathered crystals, which bore 
* A fine jaw of which is figured by Prof. Marsh in this paper. 
