780 General Notes. 
lastly, entirely absent. The other genera of the family—of whi¢ t 
a Synopsis is given—are Seison of Grube, with two species, a 
Saccobdella of Van Beneden and Hess, with a single species 
Mo ttuscs.—Prominent among the papers in the twenty-sixth 
volume of the Yournal de Conchyliologie, just completed, may be 
mentioned an account of the Molluscan fauna of the valleys d 
the Tage and the Sado, Portugal, by Nobre; descriptions of nev 
species of Molluscs from Annam, by Wattebled; from ambodi f 
and Tonkin, by Morelet ; and from China, by Hende. 
EMBRYOLOGY. 
A Theory of the Origin of Placental Types, and on cer | 
Vestigiary Structures in the Placentz of the Mouse, Rat, by 
Field~Mouse.—The discoidal placenta has been suppose d | 
Balfour to have been derived from an earlier and less spe seen 
He, however, gave no connected, and, as its% E 
to the present writer, no plausible view as to the met me i 
gested by me. iat 
> The view which the writer holds is essentially as at 
(1) 2 by Primitive form of the placenta approxi mated that 0 
d on diffuse type. 2) The primitive type of pone 
oe nate bipartite, and its cornua were therefore tubu n 
Faces Ari in one of the cornua of such an uterus, ch tie 
os ere enlarged, must have caused the latter to tou ase 
uterine mucosa aroun or, just ; 
eek pU into a flexible tube would be in annular Cte 
ah 
mucous membrar a 
F Elite by Yous a i versity t E 
sylvania, Pha leioy RYDER, Ph.D., Biological Department, Universi? a 
