7 i8 



MAMMALIA. 



-shaped interclavicle, the whole girdle resembling that 

 of Lizards. An interclavicle is, however, recognisable in 

 the embryos of some Placentals also. In Ornithorhynchus 

 the ischia form a long ventral symphysis ; in Echidna the 

 acetabulum socket for the femur is incompletely ossified 

 (reminding one of Birds, though it is only a secondary 

 peculiarity) ; the pubes bear epipubic bones, as in Mar- 

 supials. On the side of the tarsus, in the duckmole, there 

 is a spur perforated by the duct of a gland. This spur is 

 well developed in the males, but rudimentary in the females. 

 The male Echidna has a similar but smaller spur. The 



fibula has a proximal process like an 

 olecranon. 



The brain is smooth in the duck- 

 mole, convoluted in Echidna ; the 

 cerebellum is not covered by the 

 cerebrum, there is a large anterior 

 commissure, and the corpus callosum 

 is rudimentary or absent. 



The food canal ends in 



a 



FIG. 352. - Pelvis of r , 



Echidna. FromEdin- 1 he right aunculo - ventricular 

 burgh Museum of valve in Omithorhynchus is partly 



muscular as in Birds, while in other 

 Mammals it is membranous and 



Science and Art. 



o.f., obturator foramen be- worked by papillary muscles attached 



tween ischium and pubis , J \ . r, , , , , 



(/>.). to it by tendon-like cords (chordae 



tendineae). The temperature of the 



blood is about 25-28 C., and is noteworthy in being 

 unusually variable. 



The ureters open, not into the bladder, but into the 

 urogenital canal, as they do in the embryos of higher 

 Mammals. 



The testes remain in the abdomen. The left ovary is 

 larger than the right, as in Birds. The vasa deferentia 

 open separately into the urogenital canal. So in the 

 female do the oviducts, and these have no fringed fim- 

 briated apertures nor distinct uterine region. The penis is 

 attached to the ventral wall of the cloaca, and the uro- 

 genital canal communicates both with the cloaca and with 

 the canal of the penis. The whole structure resembles in 



