ORTMANN : TERTIARY INVERTEBRATES. 
59 
male form is more frequent and most pronounced in the largest individ- 
uals, seems to furnish some support for this assumption. On the other 
hand, the comparatively much rarer occurrence of the alate form does not 
favor this view, since it is hard to believe that males were so very much 
less in number than females, that even in some localities they have not 
been found at all. The actually small number of the alate individuals in 
our collection is not accidental, since Mr. Hatcher informs me that he has 
picked up every single one that he found, and that it is really very rare as 
compared with the rotundate form. The final settlement of this question 
depends on the demonstration, that in other Scutellids the male and female 
sexes show analogous differences in form. In this respect I may point 
out here a case I have noticed: Bazin (1884, p. 38, pi. 2, f. 1-5) describes 
from the Miocene beds of Saint Juvat, Bretagne, two species of Scutella, 
S. faujasi Defr. and S. circularis Baz. The latter differs from the former 
just in these two characters, more circular form and smaller size, and per- 
haps S', circularis is nothing but the female of S. faujasi. The same may 
be the case in S', subtetragona Grat. and S’, striatula M. de S. (see Agassiz 
and Desor). 
Our young individuals show a position of the anus that has not been 
observed before.* It is distinctly marginal. Although lying on the lower 
side of the test, its posterior margin coincides with the posterior margin 
of the test. This condition prevails in all (seven) of our specimens of 
less than 27 mm length ; the first two that show the anus a little distant 
from the margin or ^4 its diameter) are 28 mm in length, but again 
in 4 specimens of 29, 29, 32, and 34 mm in length the same marginal 
position is to be seen. From 35 mm in length upward the anus is always 
removed from the margin, and the distance increases slightly with age, 
although there are variations. The smallest specimen in which it is dis- 
tant its own diameter is 36 mm long, the smallest in which it is distant 
twice its diameter is 57 mm. In the largest the distance varies from one- 
half to twice its diameter. 
Record of specimens : San Julian, Oven Point; 20 sp., 9 of which are 
young, 1 of them showing traces of the alate form, the rest are rotundate. 
Shore of Salt Lake ; 9 sp., 5 young ones show traces of the alate form, of 
the rest 1 is rotundatus, the rest alatus. Upper Rio Chalia; 18 more or 
less complete specimens, numerous fragments. 1 of medium size is 
slightly alate, the rest rotundate. Thirty miles north of Rio Chalia ; 6 sp., 
