Nomenclature of the Foraminifera. 205 



son has figured two specimens of Frondicularia (regarded by 

 him and Mr. Jeffreys as being recent, but most probably, we 

 think, derived from the chalk cliffs) from the coast of Kent. 

 In the sea-sand from Kimini worn specimens of F. comj)lanata 

 occur ; some, however, are not more worn than many of the 

 undoubted Planularia Cymha so common in, and chai-acteristic 

 of, the Rimini coast, while others are filled with ferruginous clay, 

 and have been derived from Subapennine strata. 



If we go back to the Liassic period, we find the Nodosaria 

 (then forming a large proportion of the Rhizopodous fauna in 

 certain clays) presenting innumerable gradations through some- 

 what flattened forms of Nodosaria {Lingulin(e) into true Frondi- 

 cularice, and through them to Flahellina, Planularice, and Cris^ 

 tellarm. It seems as if, in later times, these minor varieties 

 have become more specialized as to locality; and nowadays, 

 having gradually lost its potency as a genus, Nudosarina seldom, 

 in any recent deposit, shows such comprehensive suites of vary- 

 ing forms as we find in the Lias, one subspecies now predomi- 

 nating over the others in the several Rhizopodal faunae. 



As regards size, the largest individuals of all the Nodosarine 

 group are found in the Tertiary deposits above referred to, — the 

 recent Jamaica specimens (dredged by the late Mr. L. Barrett 

 in from 100 to 250 fathoms) alone rivalling them. 



The passage from Frondicularia to Flahellina is very easy, as 

 may be seen in many specimens from the Cretaceous and other 

 deposits, in which the eccentricity of the primordial chamber is 

 so slight, or, in other words, the tendency to coiling so weak, 

 that the distinction between Frondicularia and Flabellina can 

 scarcely be said to exist in them, the shell in other respects 

 presenting the general characters common to the two forms. 

 Flahellina is to Frondicularia as Marginulina and Vaginulina are 

 to Nodosaria and Lingulina ; that is, the shell is dimorphous, 

 having had two successive plans of growth — the first spiral, like 

 that of Cristellaria, the later rectilinear, like that of Nodosaria. 

 The FlabellincE of the Gault and Chalk-marl rival the largest 

 Frondicularia, and have been figured and described byD'Orbigny, 

 Reuss, and others. Pahnula sagittaria, Lea (Contributions to 

 Geology, 1833, p. 219, pi. 6. f. 228), from the Cretaceous de- 

 posits of Timber Creek, New Jersey, is either a Frondicularia or 

 Flabellina, almost certainly the latter ; for, although the early 

 chambers are not shown, the later chevron- shaped chambers are 

 not quite symmetrical. Planularia cuneata, S. G.Morton (Journ. 

 Acad. Nat. Sc. Philadelphia, 1842, viii. pi. 11. f. 5), from the 

 Middle Cretaceous Limestone of New Jersey, is also most pro- 

 bably a Flabellina, closely resembling Fl. ovata, Miinster, sp. 

 Reuss has pointed out that Von Miinster^s Frondiculince are 



