105 



TWO NEW SPECIES OF CASSIDUUMA. 



By Henry Sidebottom. 

 (^CovLvmnicatecl hy Mr. Arthur Eavland, Octoher 2otIi, 1010.) 



Carpenter states in liis Introdaction to the Stiichj of tlte 

 Foraminifera that the " genus Cassldidina was first established 

 by M. d'Orbigny, in 182G, for a peculiar type which does not 

 appear to have been recognised by any previous observer." 



He states tliat " the texture of the shell of Cassididina is 

 hyaline and finely porous, like that of the smaller Bidiminae ; and 

 it resembles that type also in the character of its aperture. In 

 fact, if we imagine a biserial Bidhnimt to be completely rolled 

 upon itself, so as to form an equilateral or nearly equilateral 

 spire, we should have the essential features of a Cassidnlina. 

 The arrangement of the chambers, as it shows itself externally, 

 lias a semblance of irregularity which does not really belong to it ; 

 the apparent irregularity being really due to the interdigitation 

 of the chambers of the two alternating series, some of which may 

 be made to appear by the obliquity of the spire as if they were 

 small and intercalated." 



Carpenter also states : " In the finely porous texture of its shell 

 and its slit-like aperture, it is obviously more allied to Bulimina 

 than to Textidaria ; whilst in the biserial interdigitate arrange- 

 ment of its chambers, it is more closely akin to Textidaria than to 

 the typical Bulimina.^' 



Brady, in the Chcdlenger Report, writes : " The distribution of 

 living Gassididinae is world-wide, almost irrespective of latitude 



