Miliolinse and in other Foraminifera. 405 



take the arrangement that they have in the other form (A, 

 with a large initial chamber) of each of the two genera, 

 namely on two planes or surfaces of symmetry for Biloculina, 

 and on three for Triloculina. He observes (Ballet. S)c. zdoI. 

 France, vol. xi. 1886, p. 557) : — " In the three species of 

 Adelosina under notice and in the three groups of Biloculince 

 already mentioned the form B presents a special character 

 common to all the individuals of each of the groups. In the 

 Adelosince this is a megasphere, completely enveloped by 

 the first chamber, which becomes lenticular. In the Bilocu- 

 lince it is the megasphere with two series of chambers on 

 two planes of symmetry. I could cite also the Triloculince 

 and the Quinqueloculince, in which the megasphere is 

 ench'cled with three, or with five series of chambers. 



" In the form B of these four genera, on the contrary, the 

 microsphere is always encircled with a cycle of five chambers ; 

 and this grouping is sometimes regularly or irregularly per- 

 sistent, and sometimes it is differently arranged. 



" I conclude, then, that, in the classification of the Milio- 

 lidas, a megaspheric form (A) will determine the genus and 

 the microspheric (B) the species." He also mentions that 

 many of the Quinqueloculince are of the genus Adelosina. 



Signor Fornasini observes that the form B in general is 

 larger than the A form, and has the microsphere succeeded 

 by more numerous chambers than in the corresponding A 

 form of the species. Also that Biloculina has the first set 

 of chambers, in B, arranged on the quinqueloculine, the 

 second on the triloculine, and the last on the biloculine planes 

 of symmetry, and that in Biloculina bulloides the microsphere 

 is succeeded by numerous chambers, arranged at first as 5, 

 then as 4, next as 3, and lastly as 2. 



The thickening of the shell- walls in various degrees, forming 

 labyrinthic interiors and cribriform apertures, already noticed 

 in Miliolidse, as in Lituolidae and other Foraminifera, has 

 been further illustrated by MM. Munier-Chalmas and Schlum- 

 berger, whether it be formed by the outside of the chamber 

 last invested or by a subsidiary and intermediate shell-growth. 



As the recognition of the separate species and varieties 

 for general purposes can, for the most part, be based on the 

 external features of the test, and these are liable to a wide 

 range of variability in individual growths, there is little need 

 of altering the names as given in most of the current litera- 

 ture on Foraminifera, and as used in the ' Monograph of the 

 Foraminifera of the Crag ' (1866), of which Part ii. is now in 

 preparation, except with regard to Triloculina and Quinque- 

 Loculina (pp. 7-14), the necessity for which change the 



