MAMMALIA. 491 
Other skeletal peculiarities must be noted, The pelvis 
bears a pair of efipudbic bones similar to those of the MJeta- 
theria, and at least in Echidna the acetabulum is incompletely 
ossified. The cervical ribs are incompletely fused on to the 
cervical vertebra, and the dorso-lumbar vertebrze have no 
Fig. 336—DuUCKMOLE (Ornithorhynchus anatinus). 
(From Goutp’s Mammals of Australia.) 
epiphyses, or only traces of them. The cranial bones anky- 
lose early, obliterating all sutures,* and the rami of the 
mandible are free. There is an entepicondylar foramen in 
the humerus. 
The temperature of the body is low and inconstant. In 
all these features the Profotheria show a low grade of struc- 
ture approximating to the reptilian. type. 
* The young Ornithorhynchus is said to possess Are- and fost-frontal bones. 
