. REPOET ON THE FORAMINIFERA. 
XXI 
has been already adverted to. Shells so constructed are generally characterised by their 
thick walls and relatively large proportion of cement, the cement itself consisting almost 
entirely of carbonate of lime. 
Little remains to be said concerning the Globigerinid^e, Lagenidjs, and Kotalida:, 
as they belong for the most part to the category of the minuter forms, of which it is almost 
impossible to obtain samples sufficiently pure and clean for satisfactory analysis. Mr. 
Murray, however, reports that a considerable bulk of pelagic Globigerince, collected by 
means of the tow-net, were dissolved by hydrochloric acid, leaving no residue whatever. 
Less difficulty is experienced with respect to the Nummulinida;, inasmuch as many of 
the species are plentiful and the individual shells of comparatively large size. Analyses 
are appended of Amphistegina lessonii and Operculina complanaia, two good represen- 
tative types. The specimens of the former were procured from the Cape de Verde Islands, 
those of the latter from near Amboyna. 
Silica, ..... 
Amphistegina lessonii. 
0-30 
Operculina complanata. 
0-2 
Ferric oxide, .... 
trace 
0-1 
Alumina, with phosphates of lime and magnesia, 
1-95 
1-3 
Carbonate of magnesia, 
4-90 
4-8 
Carbonate of lime, with a little organic matter, 
92-85 
93-6 
100-0 
100-0 
Practically, therefore, these forms may be said to consist of carbonate of lime with 
about 5 per cent, of carbonate of magnesia. 
Y d 
(ZOOL. CHALL. EXP. — PART. XXII. 1884.) 
