Nomenclature of the Foraminifera. Ill 



quite as like some of the granulate vai'ieties of the " sinuate " 

 group. 



N. lenticularis, var. 7, is referred by MM. d'Archiac and Haime 

 to the "reticulate" group, probably with justice, and to a new 

 species. Nevertheless it much resembles their figures of N. 

 Tchihatcheffi, in every respect, 



N. lent icuko'is, var. S, is decidedly a "radiate" form, resem- 

 bling N. Ramondi, N. Guettardi, N. striata, and others, even more 

 than N. Biaritzensis, to which MM. d'Archiac and Haime refer 

 it. The differences, however, are merely varietal. 



N. lenticularis, var. e, is far more like N. Rouaulti and N. Lu- 

 casana (of the "radiate" group) than N. perforata (of the 

 "sinuate" group). 



N. radiata, N. venosa, and their allies above described, are 

 simple forms of the " radiate" group. 



Nummulina, essentially symmetrical in all its varieties, is con- 

 nected with the truly unsymmetrical species of Nautiloid Fora- 

 minifers by the unequal-sided Amphistegina, small varieties of 

 which have a striking isomorphism with the Asterigerine varie- 

 ties of Rotalia Beccarii — for instance, the Asterigerina lobata and 

 A. carinata of D'Orbigny; but the Rotalian forms seldom hide 

 their primordial cell in their successive folds, whilst this habit 

 is constant in Amphistegina, however distorted it may become : 

 thus this species never exposes its spire on both sides, like 

 Operculina, nor on one side, as in Polystomella macella and the 

 Rotalia. Heterostegina (a flattish Nummulitoid species with 

 subdivided chambers) is in external form rather more like some 

 Opei-culince, with the earlier portion lenticular, and with thin 

 marginal chambers*, than an Amphistegina; and it bears the 

 same relation to Operculina that Orbiculina does to Penero- 

 pUs ; whilst Cycloclypeus, a species next beyond Heterostegina in 

 development, is in this resj)ect analogous to Orbitolites. See also 

 Dr. Carpenter, Phil. Trans. 1856, vol. cxlvi. p. 5G5. 



16. Nautdus Calcar. Page 69. Twelve varieties. Five varie- 

 ties (a-e) : " Recent : Ilimini shore, Adriatic. Fossil : Coroncina, 

 near Sienna." 



Var. a. PI. 11. figs. a-c. Keeled, rowelled, ribbed, and um- 



* The form here referred to, with its gently hiconve.x centre and thin 

 edge, is the Amphistegina Cumingii of Dr. Carpenter, so fully described 

 and illustrated in his last Monograph (read before the lioyal Society, 

 June 17. 1858, and pubhshed in the Phil. Trans, for XSb'-J). We cannot 

 agree with this talented author in ))lacing this somewhat feebly develoj)ed 

 Nummuline form in the genus Amphistegina. For our own part, we can- 

 not, on any good ])hysiological grwmds, sc|)arate it from Operculina com- 

 planata. on the one hand, or Nummulina planuiata, on the other, which 

 latter we regard as the parental form of both. 



