Nomenclature of the Foraminifera. 473 



Orbitolites, also belonging to the family which includes the 

 Miliolitidae and their allies. 



The aperture in Vertebralina consists merely of the simple 

 opening at the end of the chamber, unaccompanied by any val- 

 vular flap ; so that in V. opercularia the aperture is a slit along 

 the peripheral margin of the last, nearly circular, chamber. 



The surface in Vertebralina is marked by delicate striations, 

 which, though attaining the strength of ribs in the thick-walled 

 and more strongly characterized shells, such as V. mucronata, 

 D'Orb. (For. Cuba, pi. 7. f. 16-19), become obsolete, but are 

 very rarely absent, in the more delicate specimens. In V. oper- 

 cularia delicate striae are visible on the early chambers. Not- 

 withstanding the striation, the surface in Vertebralina is usually 

 beautifully smooth and opalescent. It is also occasionally pitted 

 (as in some fossil specimens from Grignon) a feature very 

 constant in Orbiculina. 



V. striata, var. opercularia is known only in the fossil state. 

 Lamarck's specimen was from Grignon ; our specimen is from 

 Hauteville *. It is on the shores of Australia that we find V* 

 striata making the nearest approach to V. opercularia amongst 

 its living varieties. 



30. Ovulites elongata. Tabl. Enc. Meth. pi. 479. f. 8; Hist. 

 An. s. Vert. ii. p. 194, No. 2. " Fossil; fcrignon." 



This is an elongate-cylindrical variety of O. Margaritula. See 

 above, page 291. 



31. Dactylopora cylindracea. Hist. An. s. Vert. ii. p. 189. 

 "Fossil; Grignon." ' 



This is figured by Blainville and Defrance, Diet. Sc. Nat. 

 Zooph. pi. 47. f. 4 (thick variety), pi. 48. f. 1 (delicate va- 

 riety t). D'Orbigny has recognized it as a Foraminifer (Cours 

 Elem. Pal. et Geol. ii. p. 192); but he has grouped it with 

 his " Monostegues," and regarded it as a congener of Ovu- 

 litesj for which determination there are not the least grounds, 

 as its structure is very complicate, and to some extent allied to 

 that of Orbitolites. Bronn, in the third edition of the ' Lethsea 

 Geognost./ places Dactylopora and some other forms between 

 the Foraminifera and the Bryozoa. We may especially refer to 

 this valuable work for the synonymy of D. cylindracea and D. 

 elongata (op. cit. vol. i. pp. 256, 257), and for a list of the loca- 

 lities where they have been collected in France and Belgium. 



a & b. Varieties D. eruca and D. digit ata. In the East Indian 

 and other tropical seas we have met with some curious small 



* Since writing the above, we have met with several specimens nearly 

 approaching in form to V. opercularia in a sample of Grignon shell-sand. 



f This is termed Polytrype elongata, but is merely a smaller, more 

 slender, and less worn specimen of D. cylindracea. 



