152 Transactions of the Society. 



of the microspheric form. Some careful preparations of these tests 

 confirmed that opinion, and photographs of the sections are now 

 reproduced. 



In form A the central chamber, or megalosphere, is ovoid or 

 kidney-shape, and in the present example has a longer diameter 

 of 250 //,. The succeeding chamber is nearly spherical in optical 

 section, and is immediately followed by a series of shallow cham- 

 bers lengthened along the principal axial line, and secondarily sub- 

 divided into chamberlets, at first in a single row, and afterwards 

 increasing to two or three superposed series with intermediate 

 floors. The increasing complexity of the serial arrangement of 

 chamberlets with the growth of the shell is seen on the apertural 

 face of the test, which has a generally cribrate appearance. 



In form B the central chamber, or microsphere, has a diameter 

 of 33 fi, succeeded by two fairly short and shallow crescentic 



Pig. 31. — Triloculine series of the central disk in 

 Alveolina boscii (form B). 



chambers, and three larger, all of which are simple, as previously 

 stated of Munier Chalmas' fossil example. These chambers of 

 the central disk are arranged on the triloculine plan (see fig. 31), 

 and not on the peneropline, as Lister * infers from Schlumberger's 

 note on the fossil occurrence. Following upon these are the 

 normal chambers of the test, which extend the whole length of 

 the shell, and are subdivided into several rows of chamberlets, 

 as in form A, and showing successional increase in the number of 

 floors or horizontal partitions, as in the megalospheric type. In 

 form A, however, the segments of the convolutions are compara- 



* Loc. supra cit. 



EXPLANATION OF PLATES II. and III. 



Fig. 1. — The two forms of Alveolina boscii Defr. sp. From the Great Barrier Reef, 



(Cairns Reef), Queensland, x 1^- 

 ,, 2. — A longitudinal, median section through a megalospheric test of A. boscii. 



Great Barrier Reef, x 16. 

 „ 3. — A longitudinal, median section through a microspheric test of A. boscii. 



Great Barrier Reef, x 16. 

 „ 4. — Central area of the megalospheric form (A) of A boscii. x 184. 

 ,, 5. — Central area of the microspheric form (B) of A. boscii. x 184. 



