* 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 Sctitella, 

 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 J>. 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, i 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 i is rotundatus, the rest alatus. Upper Rio Chalia; 18 more or 

 less complete specimens, numerous fragments. i of medium size is 

 slightly alate, the rest rotundate. Thirty miles north of Rio Chalia ; 6 sp., 



