III. DESCRIPTION OF THE SPECIES. 



I. PORCELLANBA vel IMPERFORATA. 



General Characters. — Shells calcareous, imperforate, compact, and porcellaneous 

 in structure ; translucent and, when viewed by transmitted light, of a light brown 

 colour. 



Family 1.— MILIOLIDiE. 



General Characters. — Shell-structure as above, or sometimes sandy, chitinous, 

 or even siliceous. 



Sub-famih/ 1. — Miliolinin^e. 



General Characters. — Chambers two in each convolution, coiled on the long axis 

 of the shell, either symmetrically on one plane or inequilaterally ; so that two, 

 three, five, or rarely more are visible externally. Aperture alternately at either 

 end of the shell. 



Of late years much earnest research has resulted in our having a better 

 knowledge of this Agathistegian group. 



In 1826, when revising the work of previous authors, Alcide D. d'Orbigny 

 (' Ann. Sci. Nat.,' vol. vii, pp. 297 — 304) placed various forms which had been 

 included by earlier observers in the generic terms Miliola, MilioUtes, Serpula, 

 Vermicid'uni, and Lagena, into six genera, which he called BilociUina, Spiroloculina, 

 Triloculina, Articulina, Quinqiielocidina, and Adelosina, concluding that the definite 

 external segmentation of the test was of real generic importance. 



In 1858, W. C. Williamson, in his 'Recent Foraminifera of Great Britain' 

 (Ray Society), united three of the genera (Triloculina, Quinqiielocidina, and 

 Adelosina) under the one (new) name Miliolina. His chief ground for this 

 amalgamation may be given in his own words : — " This genus differs from 

 Bilocidina and Spiroloculina in the circumstance that the convolutions, instead of 

 being wound in one plane, continually alter their direction." At the same time he 



