74 FAMILY MILIOLIDA. 



hand, the progressive -widening-out of the chambers may go on to such an extent as still 

 more to disguise the fundamental type, especially when they not only become extremeh' 

 elono-ated transversely, but even wind themselves round the edges of those previously formed, 

 so as almost to meet on the opposite side of the original spire (fig. 18). Even such an 

 extremely aberrant form of the one here represented, which was distinguished by Lamarck 

 (lix and lx) under the names Benulina and Benidites* (expressive of the resemblance of 

 its shape to that of a kidney), is distinctly recognisable as a modified Vertehralina by the 

 exact conformity of the first-formed portion of the shell to the regular type, and by the 

 characteristic form of its aperture, which is a fissure extending along the entire margin of 

 the last nearly circular chamber ; and, as already pointed out (^ 89), a similar tendency is 

 common in other typical forms of this division of Foraminifera. Arrests of development at 

 the spiral condition, sometimes producing a strong resemblance to Miliola, are not uncommon 

 in either of the varietal forms of Vertehralina (figs. 17,20); and it is thus that the broad 

 specimens distinguished by D'Orbigny (xcii, pi. vii, figs. 14, 15) by the name V. Cassis, 

 have been produced. A curious dwarfed example, from a depth of 360 fathoms in the 

 Mediterranean, is represented in fig. 24. 



99. Affinitief;. — It is obvious that Vertehralina may be considered as an advance upon Nuhe- 

 cularia, alike in the symmetrical conformation of its shell, and in the more definite plan of its 

 o-rowth. In that early condition in which it is sometimes arrested, it presents a close afiinity 

 to the MilioUne type ; whilst its compressed and especially its reniform varieties bring it into 

 close relationship to Peneroplis, which it often strongly resembles in shape, being always distin- 

 guishable from it, however, by the nature of the septal aperture, and generally also by the 

 inferior lustre and opalescence of the shell. 



100. Geograpldcal Bistrihution. — Although specimens of Vertehralina are occasionally met 

 with among the Shetland islands, yet there is strong reason to believe that they have been trans- 

 ported thither from some warmer region ; as this genus seems, like Peneroplis, to belong 

 properly to tropical and sub-tropical seas, through which it is pretty generally diffused, 

 although in far less abundance than Peneroplis. ' 



101. Geological Bistrihution. — This genus presents itself in various Tertiary deposits ; 

 and it is from these that its most aberrant forms are supplied, although approximations to 

 them are furnished by their existing representatives. 



Genus V.— Miliola (Plate VI, figs. 1—33). 



103. History. — The generic term Miliolites was applied by Lamarck (lviii) in 1804 to 

 certain fossil forms belonging to a very common type, of which examples had been noticed 

 by LinnEeus (lxiii) as Serpula seminulum, by Soldani (ci) as Frumentaria, and by Montagu 

 (lxv) as Vermiculum; the designation having been apparently suggested by the resemblance 



* These names are erroneously cited by Prof. Williamson (cs, p. 44) as synonyms of Peneroplis. 



