590 REPORT—1904. 
mammals from the Santa Cruz beds, the Miocene age of which seems now to be 
sufficiently established. For nearly five years I have been engaged upon the 
Edentata of those beds, and have only recently turned to the study of the Ungu- 
lates, so that the present notice is merely preliminary. 
Dr. Roth, of La Plata, has lately published a very important paper, in which 
he shows that most of the peculiarly South American groups of hoofed animals are 
characterised by the structure of the periotic region, while two groups, the 
Litoptema and Astrapotheria, are without this character. On the other hand, all 
of the orders, including at least the Litoptema, have certain constant character- 
istics, such as the extensive articulation between the fibula and calcaneum, the 
convex distal end of the astragalus, which does not rest upon the cuboid, and 
some peculiarities in the form of the teeth. The limb and foot bones of the 
Astrapothina are not yet known, and their systematic position is, therefore, stilla 
matter of conjecture. There is a striking similarity between the dentition of these 
animals and that of the northern genera, Cadureotherium and Metamynodon, but 
the form of the skull is so radically different as to make it probable that the 
resemblance in dentition is analogical only. 
It seems likely, therefore, that Roth’s term, ‘ Notoungulata,’ may properly be 
extended to include all of the Santa Cruz hoofed animals, and that all of the 
groups which agree in the structure of the periotic region, already alluded to, 
should be regarded as sub-orders of the Toxodontia. This conception is shown in 
the following provisional table. 
NOTOUNGULATA. 
I, Toxoponvita. 
1. Toxodonta. 
2. Typotherva. 
3. Homalodotheria, 
II. Livorrema, 
III.? AsSTRAPOTHERIA, 
While these South American ungulates are singularly different from those of the 
Northern Hemisphere, it does not seem at all likely that they originated altogether 
independently of the latter. Ameghino has described a number of genera from 
pre-Patagonian formations which, though incompletely known, appear to be 
referable to the Condylarthra, the parent stock of the northern Ungulates. Very 
probably an early Eocene or late Mesozoic migration brought the Condylarthra 
into South America, and there, in almost complete isolation, they gradually gave 
rise to the various peculiar orders and sub-orders of the Notoungulata. The possi- 
bility of such migration is shown by the discovery of an armadillo in the Middle 
Eocene of North America, 
FRIDAY, AUGUST 19. 
The following Papers and Reports were read :— 
1. Heredity in Stocks. By Miss E. R. SaunDErs. 
Since the rediscovery of Mendel’s work experimental evidence: of the purity 
of the germ cells has been found in a rapidly increasing number of examples. 
Much of this evidence is derived from cases like those studied by Mendel, where 
the differentiating characters are related to each other as dominant and recessive. 
In such cases the F, generation (DR) show the dominant character, and F, 
individuals the two parental characters in the ratios 3D : 1R or 1D : 1R, accord- 
ing as they result from DR x DR or DRx R. 
In other cases the results may be complicated by such phenomena as reversion, 
