402 Prof. T. R. Jones on Dimorphism in the 



genera, namely Triloculina, Quinqueloculina, 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 Bihculina and Spiroloculina in the circum- 

 stance that the convolutions, instead of being wound in one 

 plane, continually alter their direction." At the same time 

 he pointed out that the chambers, whatever their convolutions, 

 always retain a parallelism with the polar axis of the test ; 

 also " that all the characteristic features of these genera fre- 

 quently occur in one and the same species ; " nor did he con- 

 sider a definite number of segments to be an essential feature 

 in this consolidated genus {Miliolina). 



In 1860 "Miliola" was used by Parker and Jones as a 

 comprehensive generic term (Ann. & Mag. Nat. Hist. ser. 3, 

 vol. v. p. 469) ; but, as Dr. H. B. Brady has explained 

 ('Challenger' Report, 1884, pp. 137, 156, &c), it is advis- 

 able to retain Biloculina, Fabularia, and Spiroloculina as 

 separate genera, and to keep Triloculina, Quinqueloculina, 

 and Adelosina grouped together under the name Miliolina 

 given by Williamson. These four genera constitute the sub- 

 family Miliolininas ; the other subfamilies Nubecularina?, 

 Hauerininse, Peneroplidinse, Alveolininse, and Keramo- 

 sphserinse completing the family Miliolidse. 



MM. Munier-Chalmas and C. Schlumberger, in their 

 researches on the existence of two conditions of growth in 

 many species of Foraminifera, as first indicated for Num- 

 mulites and Orbitoides by Parker and Jones (Ann. & 

 Mag. Nat. Hist. ser. 3, vol. viii. 1861, p. 233 ; Geol. Mag. 

 1864, p. 103 ; Catal. Foss. Foram. Brit. Mus. 1882, p. 93), 

 and more fully studied by Ph. De la Harpe (see letter 

 dated Oct. 1, 1879, Catal. Foss. Foram. Brit. Mus. 1882, 

 pp. 91-93; Mem. Soc. Paleont. Suisse, vol. vii. 1880-81, 

 pp. 63 &c.), discovered that such " twin forms," " couples," 

 or " dimorphs," termed by them "A" and " B," occur in 

 other genera besides Nummulites (Bull. Soc. geol. France, 

 ser. 3, vol. viii. 1880, p. 300; Compt. Rend. vol. xcvi. 1883, 

 pp. 862-866, and pp. 1598-1601 ; Ann. & Mag. Nat. Hist, 

 ser. 5, vol. xi. 1883, pp. 340, 341). Among the " Miliolidas " 

 they separated and defined, by means of carefully prepared 

 internal sections, showing the relative size of the primordial 

 chamber and the arrangement and character of the segments 

 of the test, the following forms : — Bihculina, Dillina, Fabu- 

 laria, Lacazina, Triloculina, Trillina, Quinqueloculina, Pen- 

 tellina, and Heterillina. Subsequently * ldalina, Adelosina, 



* Assoc. Franc., Congres Rochelle, 1883, pp. 230-232 ; Congres Rouen, 

 1884, pp. 520-527 ; Bullet. Soc. geol. France, ser. 3, vol. xii. 1884, pp. 629, 

 630, vol. xiii. 1885, pp. 273-323, vol. xv. 1887, pp. 573-584 ; Bull. Soc. 



