No. 408.] ORIGIN OF THE MAMMALIA. 947 
Rodentia: The types examined give negative results. 
Carnivora : A more or less distinctly tripartite condition is 
very common ; Lynx, Mephitis, Taxidea, Lutra, Gulo, Putorius, 
Bassaris (Fig. 2) show all gradations in the participation of the 
basioccipital. 
The conclusions are: (1), unlike reptiles, in no mammal does 
the basioccipital project backwards as far as the exoccipitals ; 
(2), nevertheless the participation of the basioccipital in the 
condylar articulation is a common feature, and the monotremes 
present some grounds for considering it a primitive mammalian 
feature; (3), the weight of evidence is in favor of derivation 
from a tripartite type with a depressed basioccipital. 
The evolution and gradation of the condyles in the Anomo- 
dontia (Theriodontia), from a typically monocondylic to a 
transitional dicondylic condition, in conformity with other 
mammalian structures in this order, tend to connect them 
with the hypothetical ancestral forms of mammals. Taken 
in connection also with the conditions we have been point- 
ing out among living types, the reptilian tripartite origin of 
the mammalian condyles is rendered more probable than the 
amphibian dicondylic origin. 
July 20, 1900. 
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